m 



MXMXA. 




LIBRARY OF CONGRESS, 



Cha Copyright No. 

UNITED STATES OF AMERICA. 



Shells _2 



LABORATORY GUIDE 



IN 



PHYSIOLOGY 



W1NFIELD S. HALL, Ph. D., M. D., 

PROFESSOR OF PHYSIOLOGY, NORTHWESTERN UNIVERSITY MEDICAL SCHOOL 

CHICAGO. 



WITH APPENDICES ON ORGANIZA^ 
TION AND EQUIPMENT. 



TWO COLORED PLATES 

AND 

SIXTY ILLUSTRATIONS. 



y N '^t\Ct Of *$P 

(( NOV 1 133*? 

CHICAGO: 

THE W. T. KEENER CO. 

1897. 

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Copyright, 1897, 
By Winfield S. Hall. 



PREFACE. 



American laboratories of physiology have usually been 
established in medical schools after these institutions have 
already associated histology with pathology, and physio- 
logical chemistry with general chemistry. The problems 
presented in those American laboratories of physiology, 
which are departments of medical schools, are, therefore, 
essentially the physical problems of physiology. And 
such are the problems which occupy the major part of this 
manual. The student who has but four years to devote to 
the study of medicine cannot consistently be assigned 
more than 100 hours to 120 hours of laboratory work in 
physical physiology. How to most profitably spend this 
brief period is a question which has engaged the attention 
of the writer for a number of years. 

In the choice of the work to be assigned to the student 
it has been taken for granted that he has entered upon 
his study of medicine with a working knowledge of physics 
and of Algebra, and that laboratory work in physiology is 
not begun until the student has made considerable prog- 
ress in gross and minute anatomy. Courses in anatomy 
and physiology should be so coordinated as to enable the 
student to gain a thorough knowledge of the morphology 
of an organ before he experiments upon its function. 

The method of presentation is purely inductive. The 
student is given the technique and, through a series of 
questions, he is guided in his observations. He is not, 
however, told what he is expected to observe, nor is he told 



LABORATORY GUIDE IN PHYSIOLOGY. 

what his conclusions are expected to be. On these points 
he is left on his own resources. Repeated trial of this 
method with different classes proves it to be most satisfac- 
tory both to the instructor and to the student. It gives to 
both free play for originality and individuality. 

The manual as here presented is far from complete. 
Should a second edition be justified, it will contain in addi- 
tion to the present matter, chapters on Metabolism and 
Animal Heat; Excretion; The Voice and Hearing; The Ce?i- 
tral Nervous System; and, An Introduction to Physiological 
Psychology. 

The Author acknowledges his indebtedness to the 
Chicago Laboratory Supply Co. and to Richards & Co. for 
the cuts used in Appendix C. He takes this opportunity 
to express his thanks to Dr. W. K. Jaques for preparing 
the chapter on Physiological Hematology, and to Mrs. 
Jaques for illustrating the same; to Dr. H. M. Richter for 
the chapter on Pharmacology; to Dr. A. M. Hall for the 
lessons on Normal Ophthalmoscopy and Skiascopy; and to 
Miss N. S. Hall for the illustrations of the first six chapters. 

The Author. 
Chicago, Sept. 30, 1897. 



Table of Contents. 



INTRODUCTION. 



PART I. GENERAL PHYSIOLOGY. 



A. The physiology of ciliary motion. 

I. a. Normal Ciliary Motion 16 

b. Ciliary Motion Modified by the Influ- 
ence of Narcotics and Stimulants. 
II. To Determine the Amount of Work done 

by Cilia 23 

B. The general physiology of muscle and nerve tissue. 

III. a. Elements and Conductors. 

b. Keys. 

c. Commutator. 

d. Work done by the Cell or Element. 

e. Electrical Units of Measurement 26 

IV. Batteries; Cells in Multiple Arc or in 

Series; Relation of the Current to the 
Method of Joining the Cells 30 

V. Methods of Varying the Strength of Cur- 

rent . 40 

a. The Rheostat. 

b. The Du Bois-Reymond Rheocord. 

VI. To Vary the Strength of Current through 

the Use of (a) the Simple Rheocord, or 

of (b) the Ludwig Compensator 43 



LABORATORY GUIDE IN PHYSIOLOGY 

VII. To vary the strength of an Electric. Current 

Gradually. FleischPs Rheonom 48 

VIII. To Determine the Influence of the Kathode 

and Anode Poles 51 

IX. a. The Muscle-Nerve Preparation. 

b. Indirect Mechanical, Thermal and 
Chemical Stimulation of the Gastroc- 
nemius 56 

X. Variations in the Method of Applying 
Mechanical, Thermal and Chemical 
Stimuli 61 

a. Direct and Indirect Stimulation. 

b. Qualitative Variation of Stimuli. 

c. Quantitative Variation of Stimuli. 

d. Variation of Length of Time of Ap- 
plying the Stimulus. 

XI. Electricity as a Stimulus. The Galvanic 

Current 75 

XII. Stimulation with the Constant Current. 

The Simple Rheocord , 68 

XIII. The Effect of Induced Current. Tetanus. 70 
XIV. To Determine the Amount of Work Done 

by a Muscle 73 

a. The Work Done by a Single Contrac- 
tion. 

b. The Tot'al Amount of Work Done by a 
Muscle. 

c. Reaction Changes in Fatigued Muscle. 
XV. To Determine the Effect of a Constant 

Current upon the Irritability of a Nerve. 

Electrotonus 75 

XVI. Pfliiger's Law of Contraction 80 



CONTEXTS. 

PART II. SPECIAL PHYSIOLOGY. 



C. The Circulation. 

XVII. The Circulation and its Ultimate Cause. . . 85 

a. The Capillary Circulation. 

b. To Observe the Action of the Frog's 
Heart. 

XVIII. The Graphic Record of the Frog's Heart 

Beat 89 

XIX. The Apex Beat. The Heart Sounds. The 

Cardiograph 91 

XX. The Flow of Liquids through Tubes. Lat- 
eral Pressure 93 

XXL The Flow of Liquids through Tubes under 
the Influence of Intermittent Pressure. 
The Impulse Wave; Graphic Tests ... . 98 
XXII. The Laws of Blood Pressure Determined 
from an Artificial Circulatory System. 
Pulse Tracing from the Artificial System. 1 02 

XXIII. The Human Pulse. The Sphygmograph. 

The Sphygmogram 106 

XXIV. To Determine the General Influence of the 

Vagus Nerve upon the Circulation 109 

D. Respiration. 
XXV. a. External Respiratory movements 113 

b. Intra-thoracic Pressure. 

c. Intra-abdominal Pressure. 

XXVI. Respiratory movements in Man 117 

a. The Stethograph. 

b. The Thoracometer. 

c. The Belt-Spirograph. 

d. The Stethogoniometer. 



L ABORA TOR \ G UIDE IN PHYSIO LOGY. 

XXVII. Respiration in Man 124 

a. Lung Capacity. 

b. Strength of Inspiration and Expiration. 

c. Chest Measurements. 

d. Preservation of Data. 

XXVIII. The Evaluation of Anthropometric Data. . . 127 
XXIX. The Action of the Diaphragm 132 

a. Stimulation of the Phrenic Nerve. 

b. The Phrenograph and the Phrenogram. 
XXX Respiratory Pressure 136 

a. The Pneumatogram. 

b. Stimulation of Pulmonary Vagus. 

c. The Elasticity of the Lungs. 

d. The Cardio pneumatogram. 

XXXI. Quantitative Determination of the C0 2 
and H 2 Eliminated from an Animal in 

a Given Time 140 

XXXII. Respiration under Abnormal Conditions. . 144 

a. Respiration in a small closed space. 

b. Respiration in a larger closed Space. 

c. Respiration in an Atmosphere of C0 2 . 

d. Post-mortem Examinations. 

XXXIII. Respiration in Abnormal Media 147 

a. Respiration in an Atmosphere ot Nitro- 
gen. 

b. Respiration in an Atmosphere of Hydro- 
gen. 

c. Respiration in an Atmosphere of one- 
third Illuminating Gas. 

d. Post-mortem Examinations. 
E. Digestion and Absorption. 

XXXIV. The Carbohydrates 153 

XXXV. Salivary Digestion 157 



CONTENTS. 5 

XXXVI. The Proteids 161 

XXXVII. a. The diffusibility of Proteids 166 

b. Milk. 

XXXVIII. Gastric Digestion 171 

XXXIX. Gastric Digestion, Continued 177 

XL. Gastric Digestion, Continued 180 

XLI. The Properties of Fats 182 

XLII. Intestinal Digestion 186 

XLII1. Absorption 189 

F. Vision. 

XLIV. Dissection of the Appendages of the Eye. . 191 

XLV. Dissection of the Eyeball 195 

XLVI. Physiological Optics 198 

a. Determination of the Indices of Refrac- 
tion of Water and of Glass. 

b. Determination of the Focal Distance of 
Lenses. 

c. Verification of the formula: Y+jF^ir 

d. Problems. 

XLVII. Physiological Optics, Applied 210 

a. The Application of the Laws of Refrac- 
tion to the Normal Eye. "The Re- 
duced Eye." 

b. To Locate, Experimentally, in the Mam- 
malian Eye the Cardinal Points of the 
Simple Dioptric System. 

XLVIII. a. Accommodation 216 

b. Convergence. 
XLIX. Miscellaneous Experiments 222 

a. Scheiner's Experiment. 

b. Purkinje Sansom's Images. 

c. The Blind Spot. 



LAB OR A TO R Y G UIDE IN PH YSIOL OGY. 

d. The Macula Lutea — Maxwell's Experi- 
ment. 

e. Shadows of the Fovea Centralis and 
Retinal Blood Vessels. 

L. Perimetry: The Light- perimeter, the Form- 
perimeter and the Color-perimeter 226 

LI. Determination of Normal Vision 232 

a. The Acuteness of Direct Vision. 

b. The Range of Accommodation. 

c. The Amplitude of Convergence. 

LH. Normal Ophthalmoscopy — Direct Method. 247 

a. The Emmetropic Eye. 

b. The Hypermetropic Eye. 

c. The Myopic Eye. 

LIII. Normal Ophthalmoscopy — Indirect 
Method. The Emmetropic, the Hyper- 
metropic and the Myopic Eye 250 

LIV. Skiascopy 252 

The Emmetropic, the Myopic and the 
Hyperopic Eye. 
Q. Physiological Hematology. 

LV. Examination of Fresh Blood 259 

LVI. Counting Red Blood Corpuscles — Thoma- 
Zeiss Counter 262 

LVII. Counting White Corpuscles. Decoloriz- 
ing the Red Cells 265 

LVIII. Counting Red and White Corpuscles. 

Staining the White Cells 268 

LIX. To Determine the Relative Volume of Red 

Corpuscles and Plasma. The Haematocrit. 270 
LX. Estimation of Haemoglobin, v. FleischPs 

Haemometer 273 

LXI. The Microscopic Technique of Haematol- 

ogy 276 



CONTENTS. 7 

a. Spreading Blood. 

b. Fixing and Staining. 

LXII. Differential Counting of White Cells and 

of Red Cells 280 

LXIII. Study of Bone Marrow 281 

H. An Introduction to Pharmacology. 

LXI V. Curare 285 

LXV. Atropin 290 

LXVI. Pilocarpin 293 

LXVII. Strychnin 295 

LXVIIL Veratrin 298 

LXIX. Digitalis 300 

LXX. Aconite 303 

Appendix A. 

Description of General Laboratory Appliances and 

New Apparatus 307 

Appendix B. 

On the Organization and Equipment of the Depart- 
ment of Physiology 321 

Appendix C. 

Figures and Brief Descriptions of Instruments 333 



INTRODUCTION. 



THE METHOD OF PRESENTING THE SUBJECT. 

REGARDING ILLUSTRATIONS. 

The profuse illustration of a text-book is in perfect ac- 
cord with the principles of pedagogy; that the profuse 
illustration of a laboratory manual is the reverse is evident 
from the following considerations : 

The laboratory student receives from the demonstrator 
the material with which he is to work. If he receives 
a piece of apparatus which is new to him, a few questions 
or hints in his laboratory manual will lead him to discover, 
from an examination of the apparatus itself, the physical 
and mechanical principles involved and utilized in it. 
Most students will spontaneously make drawings showing 
the essential parts of the instruments; all students will 
willingly do so if required. This is a most valuable exer- 
cise for the pupil, which is likely to be omitted if the 
manual contains cuts of the apparatus. 

Nearly every exercise requires the preparation of some 
simple appliance — e. g., a frog board or a recording lever 
— whose construction will be much facilitated if the stu- 
dent is guided by a figure in his manual, but a model 
which the demonstrator has made will be a better guide. 

I have often seen students read their text descriptive 
of some organ — e. g., a frog-heart — and verify its state- 
ments from the accompanying figures, leaving almost un- 
noticed the object itself, which lay before them. A few 
brief questions or hints would have led them to discover 



1 LAB OR A TOR Y G UIDE IN PH YSIOL OGY. 

from the object all of its essential features. Diagrammatic 
anatomical figures are sometimes useful in a laboratory 
manual, but true anatomical figures are worse than use- 
less — they bar the student's independent progress. If his 
laboratory manual contains illustrations of all apparatus 
and tissues, and of such experiments as admit of graphic 
records, the student makes similar drawings in his notes, 
either unwillingly or dependently — frequently both. The 
laboratory work is thus robbed of much of the benefit it is 
intended to give the student. Independence and origi- 
nality are completely defeated or aborted, except in the 
case of the rare student. 

If the laboratory manual contains graphic records of 
experiments, much of the time of the demonstrator will be 
consumed in explaining to the students individually why 
the same physiological functions observed with slightly 
different apparatus and under slightly different circum- 
stances, may yield tracings which differ in minor detail 
from those in the book. The energies of both demonstra- 
tor and students will thus be partially diverted from their 
legitimate channel. 

If there are no tracings in the text, students will natur- 
ally, by comparison of their tracings, discover the essential 
and the nonessential features and will seek the cause of 
the essential features of their tracings. After the student 
has made these independent discoveries he is in a position 
to gain the maximum profit from the comparison of his 
own tracings with those which others have taken, and 
from any explanations which the demonstrator may choose 
to add. 

It is evident then, that, from a pedagogical stand- 
point, the laboratory guide should be sparsely illustrated. 
On the other hand, the student's notes should be profusely 
illustrated. 



INTRODUCTION. 11 



REGARDING EXPLANATIONS. 



What has been said regarding the illustrations of 
apparatus and of results applies, in principle, to the ex- 
planation of physiological observations. As wheat is more 
valuable than chaff, so is the independent discovery of a 
principle by the student more valuable to him than its ex- 
planation by a book or instructor. If the facts to be 
observed and the principle involved be detailed and ex- 
plained in advance, the student's power of independent 
observation and investigation remains undeveloped. 

THE FUNCTION OF THE DEMONSTRATOR. 

It may be well to introduce this topic by a statement 
of what the function of the demonstrator is not. It cer- 
tainly is not to rob the student of the pleasure, exhilaration 
and benefit of the independent investigation of a problem 
by introducing each laboratory period with an enumeration 
of the facts and principles which the work of the day is 
expected to establish. Such an introduction is worse than 
useless. The desirability of even asking the attention of 
the entire class to introductory remarks on the general 
bearing of the problem in hand is to be questioned. If 
the problem is well chosen and the work in the physiolog- 
ical laboratory properly coodinated with that in the 
recitation room and lecture room and that in other de- 
partments, its significance will at once be evident to the 
intelligent pupil. If the introductory talk is omitted the 
prompt student may begin at once, upon entering the 
laboratory, the problem of the day, and will have a clear 
gain of ten to twenty minutes. Any supplementary in- 
struction or hint may most profitably and ecomically be 
written upon the blackboard. 

Most of the experiments given in this book cannot con- 
veniently be performed by one individual working alone. 



12 LA B OR A TORY G UIDE IN P// YS/OL O G Y, 

After some experimentation it has been found most advan- 
tageous to divide the class into sections not exceeding 
thirty students, and to subdivide these sections into divi- 
sions of three students each. Each division is assigned a 
table. The assistant demonstrator places the material 
needed for any day's work either upon the table or where 
it is readily accessible. 

Nothing should be done for the student which he can 
profitably do for himself. A small class with less limited 
time may easily construct much apparatus in the work- 
shop. No class is so large as to debar the members from 
the privilege of constructing frog boards, tracing levers, 
etc., (which may be done at the tables) and of setting up, 
adjusting and readjusting all apparatus. 

Nothing should be told a student which he can readily 
find out for himself. The function of the demonstrator 
is to guide the student by questions and by hints to dis- 
cover facts and to formulate principles. Extended expla- 
nations on the part of the demonstrator may instruct the 
student, but they do not educate him. 

HINTS TO THE STUDENTS. 

It is a general principle that a student gets out of a 
course what he puts into it, and with interest. If he in- 
vests (1) intellectual capacity, (2) the spirit of inquiry 
and investigation, (3) the power of logical reasoning, and 
(4) the power to formulate conclusions; he will promptly 
receive interest upon the investment. Further, the greater 
the investment the greater the rate of interest. This may 
seem inequitable, but it is inevitable. 

The value of taking full notes of laboratory experiments 
is unquestionable. The following hints regarding note 
taking may be advantageous: 

1. Make a careful description of each new instrument 
with which you work. 



INTRODUCTION. 13 

2. Formulate each problem definitely. 

3. Describe the means used in the solution of the problem. 

4. Enumerate the facts observed through the help of the 

means employed. 

5. Seek for and note causes and inter relations or the facts 

as far as possible. 

6. Differentiate the essential from the incidental. 

7. Formulate conclusions from the collected data. 

8. Make generalizations as far as they are justifiable. 

Agood note book should possess thefollowing qualities: 

a. It should be complete, containing an account of every 

problem studied. 

b. It should be full, containing a sufficient amount to 

guide another in performing the same experiments 
and in verifying the facts and conclusions noted. 

c. It should be logically arranged. 

d. It should be as neat and artistic as the student can 

make it in the time which he can devote to it. 



PART I. 

GENERAL PHYSIOLOGY OF CONTRACT. 
ILE AND IRRITABLE TISSUES. 



15 



A. THE GENERAL PHYSIOLOGY OF CILIARY MOTION. 

1. a. Normal ciliary motion, b. Ciliary motion modified 

by the influence of narcotics and stimulants. 

a. Normal ciliary motion. 

/. Appliances. — Microscope, cell slide and cover glass; 
normal saline solution (NaCl 0.6 %, Appendix 
A, 1); physiological operating case (App. A, 3); 
filter paper; frog or fresh water clam or mussel. 

2. Preparation. — If a lamellibranch be used one need only 

snip off, with the small scissors, a bit of the margin of a 
gill and mount it in a drop of normal saline solution 
on a cover slip, invert the cover over the cell of the 
cell slide and focus under low power. If a frog be 
used it will be necessary to pith it as a preliminary 
step. 
j. Operations. — To pith a frog. 

(1). Grasp it with the left hand, holding the legs ex- 
tended," one on either side of the little finger in such 
a way as to bring the dorsum of the frog toward the 
palm of the hand. 
(2). With the thumb and index finger fix the frog's 

nose and press it ventrally. 
(3). Place the point of a narrow bladed scalpel in the 
median-dorsal line over the space between the occi- 
put and atlas, i. e., over the occipito-atlantal mem- 
brane. This point is most readily located by using 
the eyes as a landmark. The occipito-atlantal mem- 
brane lies at the apex of an equilateral triangle whose 
base has its extremities in the center of the corneoz. 
Having located the point for incision, press the 
16 



GENERAL PHYSIOLOGY. 17 

knife through the skin, the intervening connective 
tissue and the occipito-atlantal membrane, and cut 
the spinal cord transverely. Withdraw the knife. 
(4) Insert the apex of a slender probe or of a blunt 
needle into the incision, turning it sharply forward 
so as to enter the cranial cavity. By sweeping the 
distal end of the probe from side to side the con- 
tents of the cranial cavity may be functionally de- 
stroyed. When it is required simply to pith a frog 
it is understood that the operation is complete as 
described above. It may, however, frequently be 
necessary to destroy the spinal cord as well as the 
brain. To accomplish this insert the needle as de- 
scribed under (4) ; but turn the point of the probe 
so that it shall enter the neural canal of the verte- 
brae. Pass it along this canal to a point nearly op- 
posite the anterior end of the ilia. Withdraw the 
probe. 

A pithed frog can suffer no pain, but will respond 
renexly to certain stimuli. A pithed frog whose 
spinal cord is destroyed cannot with the skeletal 
muscles respond reflexly to any stimuli. Having 
pithed the frog and destroyed its spinal cord, pin it 
to a frog board with dorsum down, and legs ex- 
tended. 
To remove the oesophagus of a frog. 

(1) Place the head of the frog nearer to the operator. 
With forceps lift the mandible and with the stronger 
scissors sever the whole floor of the mouth trans- 
versely and as far posteriorly as possible. Divide 
the skin in the median line as far posteriorly as the 
pubes. 

(2) Separate the two lateral halves of the sternum by 
dividing the median sternal cartilage and carry the 



18 LAB OR A TOR Y G UIDE IN PHYSIOL O G Y. 

incision through the xiphoid appendix and abdomi- 
nal walls. Withdraw the pins which fix the anterior 
extremities; separate the lateral halves of the ster- 
num by lateral traction upon the legs. 

(3) With the forceps grasp a fold of the mucous 
membrane which surrounds the puckered anterior 
end of the oesophagus. While making gentle trac- 
tion with the forceps, make, with the fine scissors, 
a circular incision through the mucous membrane 
surrounding the opening of the oesophagus. 

(4) Grasp the pyloric end of the stomach; sever the 
duodenum; lift the stomach up vertically above the 
sternum; make moderate traction. The delicate and 
elastic submucosa about the end of the oesophagus 
will yield to the traction and the whole oesophagus 
will be readily separated from the surrounding tis- 
sues and wholly removed from the frog. 

(5) Open stomach and oesophagus by means of a 
longitudinal incision through their walls; stretch 
them upon a cork board, fixing with pins, and wash 
off mucus with normal saline solution and camel's 
hair brush. Remove the excess of liquid with the 
help of filter paper. 

4. Observations. 

(1) Place a small piece of cork upon the anterior end 
of the oesophagus. Does the cork move? H so, in 
what direction and at what rate ? 

(2) Will the cork pass over the boundary line between 
oesophagus and stomach, and will it move over the 
surface of the stomach? 

(3) To determine the cause for the movement of the 
cork, cut a minute portion of mucous membrane 
from the crest of one of the folds, place it in a drop 
of saline solution as directed under 2 [Preparation] 



GENERAL PHYSIOLOGY. 19 

and examine with a microscope. If the preparation 
has been properly made the margin of the tissue 
should, at certain points, show the cause for the 
phenomena above observed. Study the character 
of the ciliary movements. Describe. 
(4) Study ciliary movement with higher power. It is 
probable that the first preparation is not suited to 
observation with a high power. If the cilia cannot 
be readily brought into focus, prepare a second one 
as follows: From the ciliated surface — clam-gill 
or frog- oesophagus — scrape a few epithelial cells, 
with the point of a scalpel, place the minute bit of 
tissue upon a cover glass; add a small drop of saline 
solution; gently tease the tissue with needles, in- 
vert the cover upon a slide, allowing one edge to 
rest upon a hair, to avoid undue pressure upon the 
tissue. 

Focus under high power (300-600 diam.). If the 
preparation is successful groups of ciliated cells 
may be seen and the character of the ciliary move- 
ment studied. 
b. Ciliary motion modified by the influence of nar= 

cotics and stimulants. 
is Appliances. — In addition to the appliances enumerated 
above under a, one needs : A gas flask and siphon as 
shown in Fig. 1. Also a cell slide with conducting 
tube. (Fig. IB.) A gas generator will be necessary 
unless there is a large generator for general use by 
the class. HC1 25%, marble, chloroform, ether, ab- 
solute alcohol, sealing wax, thread, small glass tube, 
soft parafin. 
2. Preparation. — To prepare a, cell slide with conductor. 

(1) From a hard rubber ring, having an inside dia- 
meter of about 1 cm, and a thickness of about 



20 



LABORATORY GUIDE IN PHYSIOLOGY. 



2 mm., cut a radial segment about 2 mm. wide. 

(2) Clean the ring and slide with absolute alcohol. 

(3) Fix the ring to the slide with sealing wax, placing 
the opening in the ring toward one end of the slide. 

(4) Heat the glass tube and draw it to one-half of its 
orginal diameter as shown in Fig. 1. B. 

(5) Fix the glass tube to the slide, using sealing wax. 
The tube may be further supported by a few turns 
of heavy linen thread drawn tightly, tied and fixed 
in position with drops of melted wax. 

(6) In order not to give too free vent from the cell for 




Fig. 1. Apparatus for forcing a stream of gas or vapor through a cell. 
For description, see I=b 2 and j>. 



the gas which enters by the tube a bit of soft para- 
fin may be warmed in the hand and worked, with 
the point of a scalpel, into the space around the 
end of the glass tube leaving only a little furrow in 
the parafin above the tube. 
Operation. — Fill the gas flask full of water and dis- 
place it with C0 2 gas. Fill the siphon and adjust 
apparatus as shown in the figure. During any read- 
justments of the apparatus the siphon may be kept 



GENERAL PHYSIOLOGY. 21 

filled and ready for action by putting on a screw- 
clamp at s. Through varying the height of the 
receptacle into which the siphon dips or through ad- 
justment of the screw clamp or of the spring clamp at 
d, the pressure and the rate of flow of gas are under 
perfect control. Prepare a specimen of cilia for ob- 
servation with a low power microscope. Bring a good 
specimen into the field, focus the microscope and ob- 
serve the rate and character of ciliary movement. 
Remove screw clamp at s. 
4. Observations. — a. The effect of CO 2 upon ciliary activity. 

(1) While observing closely the normal action of the 
cilia, press the spring clamp gently for a few mo- 
ments. If after a half minute or more no noticeable 
change takes place in the rate of movement of the 
cilia repeat the dose of gas. 

What is the effect of C0 2 gas upon the activity 
of cilia ? 

(2) After the effect of the gas has become apparent, 
clamp the tube at d; disjoin at glass tube beyond and 
gently draw air through the cell, thus ventilating it 
and restoring practically the normal condition. Do 
the cilia resume the normal movement ? 

(3) How many times may the cilia be narcotized to 
the point of complete cessation of activity and then 
by ventilation be revived again ? 

b. The effect of chloroform gas upon ciliary activity. 

(4) Clamp tube at s \ remove flask from apparatus, fill 
flask with water to expel C0 2 ; empty; drop into 
the flask a pledget of cotton saturated with chloro- 
form, replace flask as in Fig. 1. Make a new 
preparation of cilia and observe normal movement. 

Allow the chloroform gas to flow for a moment 



22 LABORATORY GUIDE IN PHYSIOLOGY. 

into the cell. Note the effect of chloroform upon 

ciliary activity. 
(5) How many times may the cilia be narcotized with 

chloroform and revived again through ventilation ? 
^6) Repeat (4) with ether in place of chloroform. 
(7) Repeat (5) with ether in place of chloroform. 
t\ Determine the action of alcohol vapor upon cilia. 



If. To determine the amount of work done by cilia. 

/. Appliances. — Physiological operating case ; frog board ; 
cork board 10 cm. long by 5 wide; a centimeter rule; 
a block of wood 4 or 5 cm. in height ; a bit of sheet 
lead 1 mm. thick; scales correct to a milligram should 
be accessible to the student. 

2. Preparation. — Pith a frog and destroy cord. Dissect 
out oesophagus and stomach as directed in lesson I. 
Fix to cork board so that the long axis of the cesoph 
agus shall be parallel with the long axis of the board. 
Cut a piece of sheet lead just 5 mm. square and 
another 3 mm. square. Weigh each of them. 

j. Operation. — Wash off ciliated surface, remove the sur- 
plus moisture with filter paper, and place the lead 
gently upon the anterior end of the oesophagus. 

The incline of the ciliated surface may be changed 
by resting it, at different angles, against the block of 
wood as shown in Fig. 2. 

4. Observations. 

(1) Jf the preparation is successful the piece of metal 
will be slowly carried up the incline. Should it fail 
a thinner piece of lead or a new preparation may 
succeed. With a given incline, is the small piece of 
lead carried more rapidly than the large piece? 

(2) If W = work done, g = weight in milligrams and 
h — height in millimeters, then W = g X h 
would give the work in milligram-millimeters. 

(3) Determine the distance through which the weight 
is carried in a unit of time [one minute is a con- 

23 



21 



LABORATORY GUIDE IN PHYSIOLOGY. 

venient unit of time to use], when- the incline is 
placed as shown in the figure. 

(4) With the apparatus so adjusted what is the value 
of h when the distance which the weight moves is 1 
cm. ? 

Does the thickness of the cork board need to be con- 
sidered ? 

(5) What is the work per minute, expressed in milli- 
gramm-millimeters ? 




Fig. 2. 

Fig. 2. Appliances for changing the angle cf inclination of the 
ciliated tissue. 

(6) What is the ' work done expressed in ergs? 
[1 erg = 1 dyne X 1 centimeter; 1 dyne = 1 gramme 
-*- 981] 

(7) Using the same incline compare the result in 
work done per minute with the two different weights? 
Account for the results ? 

(8) Using the weight which gave the larger values in 
the foregoing experiments, find the degree of in- 
cline which will yield the greatest amount of work ? 



GENERAL PHYSIOLOGY. 25 

(9) What significance has the variation of the thick- 
ness of the lead weight? Determine the upper 
limit of thickness? 

(10) Would it be possible to determine the amount 
of work accomplished by each cilium ? By each 
stroke of a cilium ? 



B. THE GENERAL PHYSIOLOGY OF MUSCLE AND 
NERVE TISSUE. 



III. Demonstration : a, Elements and conductors; b, Keys; 

c, The commutator; d, Work done ; e, EIec= 

trical units. 

The function of muscle tissue is to contract. Skeletal 
muscles contract only in response to stimuli. Stimuli may 
act upon the muscle tissue — direct stimulation — or upon 
the motor nerve which supplies the muscle — indirect stimu- 
lation, To study the functions of muscle and nerve tissue 
one requires to have at command various methods of stim- 
ulation. It is usual to apply mechanical, thermal, 
chemical and electrical stimulation. Experience has 
shown that of all these means electricity is the most valu- 
able, because it is subject to the greatest number of varia- 
tions in strength and in method of application. Before 
entering upon a study of the responses of irritable tissues 
to electrical stimuli it is essential to make a short study 
of the appliances used. As many of these appliances 
have been used by the student in the physical laboratory 
it will be taken for granted that he is familiar with the 
principles involved in their use. 

I. Appliances. — 2 Daniell elements or cells; wires; contact 
key; Du Bois Reymond key; mercury key; commuta- 

26 



GENERAL PHYSIOLOGY. 27 

tor; sulphuric acid, 10%; copper sulphate, saturated 
solution; mercury. 
Experiments and Observations. 
a. The Daniell cell. — Present the four parts of the 
cell. Half fill the outer receptable of the cell with the 
saturated copper sulphate solution. Put the copper 
plate into the cell; half fill the porous cup with the 
dilute sulphuric acid, lower the zinc plate carefully 
into the cup. The plate is of commercial zinc with 
its various impurities. 

(1) Observe the vigorous chemical action in porous 
cup. Write the reaction. It is evident that the 
zinc will be quickly consumed if allowed to re- 
main in the acid and this will be the case whether 
or not the cup and zinc plate be made a part of 
an electric cell, and whether the cell be acting or 
resting. 

(2) The amalgamation of the zinc. [See also App. 
A. -4.] Lift the zinc plate out of the acid, dip it 
into the mercury. The mercury adheres to the 
zinc, mingles with the surface layer of zinc, form- 
ing an alloy, with a brush or an old cloth one 
may rub the mercury over the whole surface of 
the zinc plate — the zinc is amalgamated. The 
impurities of the zinc do not enter into the alloy. 
In this way only the pure zinc which forms a part 
of the alloy is presented to the acid. Chemically 
pure zinc is acted upon very slowly by 10% 
sulphuric acid; join a wire to the exposed end of 
each plate. Touch the tongue with the freed end 
of each wire separately; touch the tongue with 
both wires simultaneously. Record results. 

(3) Place the porous cup with the zinc plate in the 
receptacle holding the CuS0 4 with the copper 



28 LABOR A TOR Y G UID E IN PHYSIOL OGY. 

plate. Touch the tongue with one wire, then with 
the other. Touch the tongue with both at once. 
Bring the two free ends of the wires into contact 
with the binding posts of a detector; note results. 
Touch the ends of the wires together, if the condi- 
tions are favorable a minute spark may be seen 
on touching and on separating the two poles. What 
conclusions are to be drawn? 
(4) Define element or cell as used in this connection . 
Define plate, pole, electrode. The zinc is arbitra- 
rily taken as the positive plate and the copper as 
the negative plate. The pole which is attached 
to the negative plate is the positive pole, and that 
which is attached to the positive plate is the nega 
tive pole. The positive pole or electrode of a gal- 
vanic cell or of a battery is called the anode, while 
the negative pole or electrode of a cell or of a bat- 
tery is called the kathode. . 

b. Keys. — (1) Show and describe the simple contact 
key (Fig. 1-k), the mercury key (Fig. 3), and the Du 
Bois-Reymond key (Fig. 4). 

(2) Two ways of using the Du Bois Reymond key. 
1st. As a simple contact key (PL I Fig 1.) 
2d. As a short circuiting key (PI. I Fig. 2.) 

c. The commutator. — Most convenient for the physio- 
logical laboratory is Pohl's commutator (Fig. 5). 
This instrument may be used for the following pur- 
poses: 

(1) To change the direction of the current. Set 
up apparatus with cross bars in place as 
shown in PI. I Fig. 3. Which is the anode 
when the bridge is turned toward a b? Which 
is the anode when the bridge is turned toward 
c d? 



GENERAL PHYSIOLOGY. 



29 



(2) To change the course of. the current. Set up 
apparatus with crossbars removed, as shown 
in PI. I Fig. 4. What course will the current 
take when the bridge is turned toward a, b ? 
What course when the bridge is turned toward 
c, d? 

(3) Pohl's commutator may be used as a simple 
mercury key (PI. I Fig. 5). Is the current open 





Fig. 3. Fig. 4. 

Fig. 3. The mercury key. Fig. 4. The DuBois- 

Reymond key. 

or closed when the commutator bridge is turned 
toward a? How may the current be opened or 
broken ? 
d. Work done by the cell. — The experiments performed 
show that the galvanic cell may under proper con- 
ditions, liberate energy. This energy is called elec 
tricity. But the immediate source of the particular 



30 



LABORATORY GUIDE IN PHYSIOLOGY. 



electric energy liberated in the foregoing experi- 
ments is the latent chemical energy represented in 
the plates and liquids of the cell. 

Under the conditions produced in the working 
galvanic cell the latent chemical energy is trans- 
formed, and at the same time liberated as electric 
energy. This liberated electric energy may make 
itself manifest in the contact spark, in moving the 
detector needle or in lifting the armature of a mag- 
net. In the last case mentioned it would not be 
difficult to determine the amount of work done, 
though it might be somewhat difficult to determine 
the amount of work which a cell is capable of per- 




Fig 5. 
Fig. 5. Pohl's commutator. For description and uses see III=C. 



forming in a given time. If one were to weigh the 
copper plate ' before and after using the cell, one 
would find that it had increased in weight. This 
increase in weight is an index of the amount of 
chemical action in the cell — of the latent chemical 
energy which has been transformed into electric 
energy. It must be, then, at least an approximate 
index of the electric energy liberated. An exact 
index of the amount of current is afforded by the 
amount of electrolysis. For example, if the nega 
tive pole of a cell be attached to a silver or platinum 



GENERAL PHYSIOLOGY. 31 

Cup containing pure nitrate of silver, and the posi- 
tive pole be attached to a piece of pure silver which 
is immersed in the silver nitrate solution, it will be 
found that one ampere of current will uniformly de- 
posit 0.001118 gm. of silver upon the cup in one 
second of time. This brings us to the question of 
the units of electrical measurements. 
Electrical units. — The electrical energy available at 
any point in a circuit, i.e., the current, as it is called, 
is, according to Ohm's law, equal to the liberated 
energy — the electromotive force — divided by the 
total resistance of the circuit. This is expressed in 
Ohm's formula, C = ^il; C =. I It is im- 
possible for the physicist to make any progress in 
the study of electrical energy without arbitrarily 
assuming units of measurement for current, for 
electromotive force and for resistance. 
(1) Current is measured in amperes. A current of 
one ampere deposits upon the negative electrode 
of a galvanic cell or battery 0.001118 gm. of silver 
per second, or 4.025 gm. per hour. [See above ] 
A concrete idea of the ampere may be gained 
from the fact that the small sized Daniell cell 
produces a current of about % ampere when the 
external resistance is reduced to a minimum. 
(3) Resistance is measured in ohms. An ohm is 
that amount of resistance, opposed to the trans- 
mission of electrical energy, by a column of mer- 
cury 1 sq. mm. in cross section and 106.3 cm. 
in length. For general purposes an ohm re- 
sistance is that of a pure silver wire 1 mm. 
in diameter and 1 meter in length. 
(3) Electromotive force is measured in volts. 

A volt is that amount of electrical energy which 



LAB OR A TOR Y G UIDE IN PHYSIOL OGY. 

will produce 1 ampere of current after overcom- 
ing 1 ohm of resistance. 

" The ohm, the ampere and the volt are thus closely 
related, and if any two of them be known with ref- 
erence to any particular electric circuit or portion 
of a circuit the value of the third may be readily 
inferred."— [Daniell]. For if C=| then E = CxR 
and R = £- Tne same relations may be expressed thus: 

1 ampere current ^ J™£,*^ - ^ ™P<*^m 
Therefore (1) Volts = AmperesxOhms. 

(2) Amperes = Volts-5-Ohms, 

(3) Ohms = Volts-*-Amperes. 

The small Daniell cell has about 1 volt E. M. F. 
and 4 ohms resistance, the current from such a cell 
is then equal to approximately ^ ampere. 

There are numerous other units of measurement 
used by physicists and electricians, but for our pur- 
pose it is not necessary to review these more 
specialized points. 



GENERAL PHYSIOLOGY. 



33 



Z^^3^^ 




^^t 



^J^ 






Plate I. 



IV. Demonstration : Batteries. 

A battery is a group of two or more elements or cells 
arranged to produce increased or multiple effect. If one 
wishes to use a stronger current than that afforded by one 
ceil, his first thought is to increase the number of cells, or 
to procure a larger cell. Experimentation will show him 
that it is not a matter of indifference which of these courses 
to pursue. In the first place if he attempts to satisfy the 
conditions he will find that to increase the size of the cell 
increases the current only when the external resistance is 
relatively small, and furthermore, there are practical limi- 
tations to the size of a cell and these may be much within 
the requirement which the cells must satisfy. It be- 
comes apparent, then, that he who would use electrical 
energy beyond the most limited field must resort to a bat- 
tery composed of a number of cells. The problem which 
first confronts him is, how shall these cells be arranged 
/. Appliances. — 6 Daniel cells; wires; detector, (Fig. 6) 
composed of simple magnetic needle mounted over 
circle divided into degrees; rheostat or resistance box, 
representing at least 100 ohms. 
2. Experiments and Observations. 

(1) (a.) Join up apparatus as shown in PL I., Fig. 6. 
With the plugs all fixed in the rheostat, i. e., 
with no resistance except that of the wires and 
battery, and the indicator needle at 0°, open 
the key and then observe the angle at which 
the needle comes to rest. 
(£.) Remove from the rheostat the plug which will 
throw into the circuit an extra resistance of 10 

34 



GENERAL PHYSIOLOGY. 



35 



ohms. Allow the needle to come to rest and 
note angle ? 
(V.) Remove from the rheostat plugs which will 
represent in the aggregate 100 ohms of extra 
resistance. Note angle of indicator as before. 
(2) Join up two cells in multiple arc as shown in PL I., 
Fig, 1. That is, join both copper plates to one 
copper wire and both zinc plates to another. 
These wires are to be carried to key, rheostat and 
detector as shown in PI. I., Fig. 6. 
{a.) Note angle of needle with no extra resistance. 
(b.) Note angle with 10 ohms extra resistance. 
(c.) Note angle with 100 ohms extra resistance. 




Fig. 6. 

Fig. 6. Detector, composed of simple magnetic needle mounted 
over a graduated circle. The two heavy, copper wires which encircle 
the compass offer slight resistance to the electric current. 



(3) Join up four cells in multiple arc or "abreast" and 

repeat the observations of angle at the three re- 
sistances as above. 

(4) Join up six cells in multiple arc and repeat observa- 

tions with 0i2, 10/2, and 100/2 resistance. 

(5) Join up two cells in series as shown in PI. I., Fig. 

8. That is, join the copper of the first cell to the 
zinc of the second. The first cell will have a zinc 
uncoupled and the second will have a copper 



36 LABOR A TOR Y G UIDE JN PHYSIOL OGY . 

plate uncoupled. These two uncoupled terminal 
plates of the battery are the ones from which to 
lead off the wires to the other apparatus, which 
should be arranged as shown in PL I., Fig. 6. 
Repeat the observations on the angle of deviation 
of the needle, using the 0D>, lOfl and 100/2 
resistance as above. 

(6) Join up four cells tandem or in series ■, and repeat 

the three observations. 

(7) Join up six cells in series and repeat observations. 

(8) Tabulate results and draw conclusions. 

1. There is a marked difference in the results of the 
two methods. 

2. With low external or circuit resistance the current 
as indicated by the angle at which the detector needle stood 
increased with an increase in the number of cells joined in 
multiple arc or abreast. 

3. With high external resistance the strength of the 
current does not seem to be essentially increased by in- 
creasing the number of cells joined up abreast. 

4. With low external resistance the strength of the 
current is not increased by adding cells in series. 

5. With high external resistance the strength of current 
increases with an increase in the number of cells joined 
up in series or tandem. 

The following theoretical points are worthy of note : 
The general formula C = g does not differentiate le 
tween that part of the resistance furnished by the battery 
and that part furnished by the external circuit. The 
former is called internal resistance (ri) and the latter is 
called external resistance (re). So we may write 
R = ri+re and C =— S 



ri+re 



GENERAL PHYSIOLOGY. 37 

Case I. 

Suppose that the external resistance is so great in 
comparison with the internal resistance that the latter may 
be made equal to zero (ri = 0) C'~ ri ^ re — —■ for one cell. 

Suppose that we arrange a battery of sixteen cells in 
multiple arc. Experiment has shown that when a battery 
is so arranged the internal resistance of the battery de- 
creases in proportion to the number of cells and that join- 
ing up cells in multiple arc is equivalent to simply increas- 
ing the size of the plates. 

Our formula then becomes : 



C'=^A- : but^L=0;C' = _E_; C= O. 
^+re '16 

Therefore no advantage is gained by joining up cells 
in multiple arc when the external resistance is incompara- 
bly greater than the internal resistance. 

Case II. 

Let the internal resistance be incomparably greater 
than the external. 

Then for one cell: C =r^-~ ; but re = 0, therefore C = -5- 

n-(-re n 

Join up 16 cells in multiple arc. The internal resist- 
ance is thus decreased by the factor 16. 

C'= -3— re = 0; therefore C'=— = 1 -^;C=16C. 

16 + re 16 

Therefore when the internal resistance is incomparably 
greater than the external resistance the current increases 
proportional with the number of cells joined in multiple 
arc. 

Case III. 

Let the internal resistance be so small relatively as to 
be discarded. For one cell C - 



ri+re re • 



38 LAB OR A TOR Y G UIDE IN PHYSIOL O G Y. 

Join up 16 cells in series. Experiment has shown 
that when cells are joined in series the internal resistance 
increases in proportion to the number of cells, for the 
current must pass through all of the cells ; further, the 
electromotive force is reinforced as it passes through each 
cell so that it also increases in proportion to the number of 
cells. Our formula then would be : 

C'= uffJL but ri = 0; therefore, C'=^E; C=16C. 

16ri+re ? J ' re ' 

Therefore the current will increase in proportion to the 
number of cells joined in series, when the external resist- 
ance is incomparably greater than the internal resistance. 

Case IV. 

Let the internal resistance be incomparably greater 
than the external and join 16 cells in series, then : 

r-, 16 E . i ... „„ ~ ,1 r r-, 16 E E 



; but re = 0; therefore C 



~ 16ri+re > > ~ 16 ri ri * 

In this case, however, C=^r: therefore there is no ad- 
vantage gained by increasing the number of cells in series 
when the external resistance is very small. 



Case V. 

Practically, however, one deals with cases where 
neither the external nor the internal resistance is so 
small as to be ignored. Let us suppose that we have a 
battery of a cells, that the internal resistance of each cell 
is r and that the total external resistance is R. It 
has been shown experimentally that the current is great- 
est when the external resistance is equal to the internal 
resistance; i. e., when — = R; s being the number of 
cells in series and m the number in rnultiple arc. 



GENERAL PHYSIOLOGY. 30 



Weh 


ave, 


then, two 


equations. 


(1) 


s r 
m 


= R. 




(2) 


s m 


= a 






Fin 


d s and m 




(3) 


s = 


a 
m 




(4) 


s = 


m R 
r 




(5) 


m 


= ^, or 


a r, = m 2 



(6) m = Vtt? or > i n a similar way, 
(6') s = V^#- 

Let us take a concrete case, using our 16 cells, each of 
which has an internal resistance of 4 ohms, how shall we 
arrange them to get the best results with 16 ohms external 
resistance. 

» = v^ = ^ = *■ 

S = ff = V^ = 8. 

We shall therefore arrange the battery in a series of 8 
pairs, each pair being joined abreast. 

How must they be arranged when there are 64 ohms or 
more of external resistance? 

How must they be arranged when there are only 4 
ohms of external resistance? 

What arrangement would you adopt if there is only 1 
ohm external resistance? 



V. Demonstration: Methods of varying the strength 

of current, a. The rheostat, b. The 

Du Bois=Reymond rheocord. 

It has already been shown that the strength of current 
may be varied by increasing the number of cells or by 
changing their arrangement in the battery. This method 
is indispensable, but it has its limitations. If one has a 
small cell and wishes to decrease the current, he must 
have recourse to another method. From the formula C = 
-|- it is evident that one may decrease the current by in- 
creasing the resistance. 
a. The rheostat. 

1. Appliances. — Resistance box or rheostat; 1 cell; 5 wires; 

detector. 

2. Experiments and Observations. 

(I) Set up the apparatus as shown in PL I., Fig. 6. 

(1) With plugs all fixed in rheostat, needle of detec- 
tor at 0°, close key and note angle of deviation. 

(2) Remove the plug which will throw into the circuit 
the lowest resistance contained in the rheostat. 
Note the angle. 

(3) Add to the above resistance the smallest possible 
increment and note angle. 

(4) Proceed in this way tabulating results. 

(5) Conclusions. 

(II) Another method of using the rheostat. The rhe- 
ostat may be used in short circuit as shown in PI. I., Fig. 
9. From this arrangement of the apparatus it is appar- 
ent that when all of the plugs are in place the current 
will be short circuited by the rheostat. If the resist- 
ance of that part of the circuit leading to the detector 
—the long circuit — be considerable the long circuit 

40 



GENERAL PHYSIOLOGY. 41 

current will probably not be sufficient to cause any 
deviation of the detector needle; for the current varies 
inversely as the resistance (C x -^-), and if the re- 
sistance of the long circuit (R) be incomparably 
greater than the resistance of the short circuit (R'), 
then the current of the long circuit (C) will be incom- 
parably less than the current of the short circuit (C'), 
i. e., C : C :: -~ : -±r, or C : O :: R' : R; therefore if 
R' = 0, C must equal 0. 

Suppose that the resistance of the detector circuit 
be only 10 ohms, and. suppose we remove from the 
rheostat plug that represents 0.1 ohm resistance, then 
one-hundredth of the current will pass through the 
detector. If we make the resistance in the short cir- 
cuit 0.2 ohms then one-fiftieth of the current will flow 
through the long circuit. 

In this way we may increase the detector current 
step by step until the maximum is reached. What 
is the maximum current to be derived when the 
resistance in the long circuit equals 10 ohms, the maxi- 
mum resistance of the rheostat 100 ohms, external re- 
sistance in circuit between cell and rheostat 1 ohm, 
E. M. F. = 1 volt, internal resistance of cell four 
ohms ? 
b. The Du Bois=Reymond Rheocord. 

In the use of the rheostat the variation of the cur- 
rent is step by step and not gradual. Experience has 
shown that lor certain physiological experiments it is 
necssary to cause a gradual variation of the current, 
i. e., an increase by infinitessimal increments. The 
Du Bois-Reymond rheocord is an instrument which 
fulfills this condition by adding to the short circuit 
millimeter by millimeter the resistance of a platinum 
wire. The principle and use of the Du Bois-Reymond 



42 LABORATORY GUIDE IN PHYSIOLOGY. 

rheocord is the same as that of the rheostat with the 
exception that one ohm resistance is furnished by two 
platinum wires which are stretched along the top 
of the long resistance box. A mercury bridge 
makes electric connection between these wires. When 
the bridge or " slider" stands at the conditions are 
the same as one has in the use of the rheostat with all 
of the plugs in. As the bridge is moved gradually 
from to 100, one ohm of resistance is as gradually 
thrown into the short circuit. At that point a plug 
representing one ohm resistance may be removed and 
the bridge brought back t'o 0, and another ohm of re- 
sistance gradually introduced into the short circuit. 
In this way any desired amount of resistance may be 
introduced by infinitely small steps — by infinitessimal 
increments— and the current of the long circuit will 
be increased correspondingly. 

/. Appliances. — 1 cell; Du B-R. Rheocord; detector; 5 
wires; key. 

2. Experiments and observations. 

(1) Set up apparatus as shown in PI. II, Fig. 1. 
With bridge at 0, close key and note angle. 

(2) Leaving the key closed gradually slide the bridge 
to 1, then slowly and with an even rate of motion 
on to 100, noting the behavior of the detector needle. 

(3) Open the key, remove the plug which represents 
1 ohm, and slide the bridge back to the zero position, 
close the key and note the angle at which the needle 
comes to rest. If the resistance of the platinum 
wires is 1 ohm then the needle will come to rest at 
the same point noted above when the bridge stood 
at 100. 

(4) From this point the needle may be caused, by 
sliding the bridge from to 100, to gradually in- 
increase its angle. 



VI. Demonstration : To vary the current through 

the use of (a.) the simple rheocord, or (b.) 

the Ludwig compensator. 

Besides the methods already used for varying the 
strength of the current one may use the derived current. 

The simple rheocord (Fig. V) may be used for this 
purpose. 

a. The simple rheocord. 

/ Appliances. — One or more cells; simple rheocord; 5 wires; 
detector. 




Fig. 7. 
Fig. 7. The simple rheocord. See also PI. II, Fig. 2. 

2. Experiments and observations. 

(1) set up the apparatus as shown in Fig. 2, Plate II. 
From the figure we see that from the cell to post 
A, thence through the German silver wire to postB 
and back to the cell makes a complete circuit. Hav- 
ing reached the metallic slider (S) the circuit has 
two paths presented. 1st, from S direct to B; 2d, 



44 LABORATORY GUIDE IN PHYSIOLOGY. 

from S through D and back to B. The total cur- 
rent is divided into two parts, C which passes 
along the wire from S to B, and C the derived cur- 
rent which passes through the detector. Sup- 
pose the resistance to the last named current is R' 
and that to the direct current is R, the relative 
strength of these two currents is expressed in the 
following proportion: O : C : : R : R'. 

But the resistance of the German silver wire may 
be conveniently divided into 100 equal parts (100 r). 

If the slider be placed at any position along the 
wire, say at x centimeters from the end, then the 
formula would be O : C : : lOOr— xr : R'. 
ri — Cr (ioo-x) 

Suppose that R = 1 ohm (r = 0.01 ohm); R' = 
2 ohms and x = 0; i. e., suppose the slider to be 
hard up to A, then O = Cr^o-x) = _c_ . Qr the 

current which passes to the detector is one-half as 
strong as the current through the rheocord. 

(2) What is the relative strength of the two currents 
when x '= 10? 

(3) What is the relative strength of the two currents 
when x = 50? 

(4) What is the relation of O to C when x — 99? 

(5) What is the relation of O to C when x = 100? 
From this course of reasoning it is evident that 

in the simple rheocord we have an instrument with 
which we can vary a derived current from zero to a 
maximum. Just what the value of this derived cur- 
rent will be will depend upon the voltage of the cell 
or battery and the total resistance to be overcome, 
as well as upon the distribution of that resistance. 

(6) Verif}' the theory just developed, making out a 
table of detector readings. 



GENERAL PHYSIOLOGY. 



45 



'T ; m J y-v- 




-^-^JSif^zziB 




Q~Z>m$ 



Plate II 



46 



LAB OR A TORY G U1DE IN PI1 YSIOL OGY. 



The Ludwig compensator. 

This instrument, though used in a. class of experi- 
ments quite different from those in which the rheocord 
is used, involves the same principle as that involved 
in the simple rheocord, and is used to make minute 
variation in the strength of a current. The general 
construction of the instrument is shown in Fig. 8. 

A f , J Soon 




Fig. 8. The Ludwig 
compensator, originally 
devised by Ludwig to 
compensate a muscle 
current, may be used 
in the same way as the 
simple rheocord. Its 
maximum current is, 
however, limited. For 
description, see VI=b. 



Fig. 8. 
The outer receptacle is of copper and serves as the 
copper plate; within is a porous cup containing the 
zinc plate. This is practically a Daniell cell. A 
graduated upright of brass makes metallic contact 
with the copper plate, and at A the circuit is com- 
pleted by a platinum wire to B. 



GENERAL PHYSIOLOGY. 47 

A slider makes contact with the platinum wire, but 
slides along the standard by an ebonite arm. The 
derived current passing along the wires A and B, and 
the direct current from S to B along the platinum wire 
sustain a relation similar to that of currents C and O 
in the rheocord. 

i. Appliances. — Ludwig compensator; 2 wires; detector. 

2. Theory, experiments and observation. 

(1) Join the two poles, a and b, to the detector; place 
the slider at cm., or hard up to the zinc plate, and 
note the deviation of the needle. 

(2) Gradually move the slider from cm. to 50 cm. 
(or 100) noting the effect upon the needle. 

(3) Suppose the detector circuit, from S through the 
detector and back to B, has a resistance of 10 ohms 
(R' = 10). Let the resistance of the platinum wire 
be 0.01 ohm per centimeter; for the instrument 
figured, R = 0.5 ohm. Let O be the detector 
current, and C the direct current. Then C : C :: 
JL : ^_ or O : C : : R : R', or C = ^- Let x be 
the distance in centimeters from B to S, or the read- 
ing of the position of the slider; then the proportion 
of R at any position of the slider would be ~^ m 
C'= ^^; substituting the assumed values, C f =~^-, 

(4) When x = how much current will flow through 
the detector? 

(5) When the slider stands at 10 cm. what proportion 
of the total current will flow through the detector ? 

(6) When the slider stands at 25 cm., how much 
larger is C than O? 

(?) When the value of x is 50 the ratio of the detector 

current to the direct current? 
(8) Verify all of these theoretical results as far as 

possible, by experiment. 



VII. Demonstration: To send an electric current into 
a nerve gradually. FleischPs rheonom. 

When one studies the effects of thermal, mechanical or 
chemical stimuli, he may apply the mechanical stimulus so 
slowly that the nerve may be severed without calling forth 
a response; he may apply heat to the fresh nerve so grad- 
ually that the nerve may be actually cooked without caus- 
ing a contraction of the muscle which it supplies. 

The problem which we have next to solve is to apply 
an electrical stimulus gradually. 

/. Appliances. — Fleischl's Rheonom; 1 Daniell cell; Du 
Bois-Reymond's " Muscle Telegraph; " contact key; 
detector; saturated solution of zinc sulphate; 5 wires; 
frog; operating case. 

The rheonom is constructed as shown in PI. II. 
Fig. 3 — R. Its essential features are: g, the non- 
conducting base with circular groove; s, the non- 
conducting rotatable, central standard; P, the battery 
binding postF, having zinc connection with the groove; 
p, the rotating, binding posts, having zinc limbs con- 
necting with the groove. 
2. Experiments and Observations. — Set up apparatus as 
shown in PL II. Fig. 3, after amalgamating the zinc 
tips which dip into the zinc sulphate. Fill the groove 
with zinc sulphate. 

(1) Find and mark the zero position for the rotating 
limbs of the rheonom; i. e., find the position which 
will give no deviation of the detector needle when 
the contact key is closed. 

48 



GENERAL PHYSIOLOGY. 49 

(2) Find and mark the position which the rotating 
limbs occupy when the detector needle indicates 10°. 

(3) Find and mark in succession each higher incre 
ment of 10° until the maximum is reached. 

(4) Rotate the limbs so gradually as to cause the de- 
tector needle to rotate with slow and regular motion 
from the zero position to the maximum position and 
back. 

(5) Make a gastrocnemius muscle nerve preparation; 
mount it in the muscle telegraph; change the wires 
from the detector to the electrodes of the muscle 
telegraph; place the limbs of the rheonom in the 
maximum position, close the key. With the closing 
of the key the maximum current is instantly thrown 
into the nerve and serves as a strong stimulus in 
response to which the muscle contracts. 

(6) Place the limbs of the rheonom in the minimum 
position. Close the key. Inasmuch as the muscle 
nerve preparation is much more sensitive to elec- 
tricity than is the low resistance detector the muscle 
will probably respond when the conditions are as 
above indicated. Theoretically a zero point exists. 
Practically it is difficult to find it for a muscle- 
nerve preparation. The finding of a position where 
there is no response on closing the key is however not 
essential in this experiment. 

(7) Keeping the key closed, slowly rotate the limbs 
of the rheonom from the minimum position to the 
maximum position. If the conditions are favorable 
this can be done without calling forth a response. 

(8) Without opening the key, slowly rotate the limbs 
backward from the maximum to the minimum posi- 
tion. One may thus send through a nerve a strong 
current and may withdraw the same without caus- 



30 LABORATORY GUIDE IN PHYSIOLOGY. 

ing a contraction of the muscle. Keep the key 
closed. 
(9) Quickly rotate the limbs from minimum to maxi 
mum; the muscle responds. Quickly rotate from 
maximum to minimum; the muscle responds. 

From the preceding observations one may con- 
clude that response to electrical stimulation is elic- 
ited not by the simple flow of an electric current 
through the irritable tissues, but by a more or less 
sudden change in the strength of the current. The 
opening and closing of a galvanic current, also its 
sudden increase or decrease, serves as an efficient 
stimulus, while the gradual increase or decrease in the 
strength of the current causes no response. 



VIII. Demonstration : To determine the influence of 
the kathode and anode poles. 

Many of the phenomena of muscle-nerve physiology 
were inexplicable until a difference was noted (Von Bezold 
1860), in the influence of the anode and kathode. This 
difference in the influence of the two poles may be best 
observed by use of the sartorius muscle of a frog. 
i. Appliances. — A double myograph and support; record- 
ing drum; Daniell cell; Pohl commutator; Du Bois- 
Reymond Key; nonpolarizable electrodes; 5 wires; 
electrode clamp and support. 
2. Preparation. 

(a) Nonpolarizable electrodes. — The Du Bois-Reymond 
nonpolarizable [N P] electrode is made as follows: 
(Fig. 9). T. Glass tube of about 4 mm. lumen. Z. 
Zinc rod with a binding screw (B). The zinc 
rod must be amalgamated before use in an electrode. 
R. Rubber tube clasping both glass tube and zinc 
rod. S. Saturated solution of sulphate- of zinc, in- 
troduced with a narrow pointed pipette. C. Kaolin 
plug, made by working china clay powder into a stiff 
paste with normal salt solution. 

The electrodes should be filled at each time of using, 
and the parts may be "assembled " in the order and man- 
ner enumerated in the description. 

(b) The Fleischl brush electrode differs from the fore- 
going in substituting the brush of a camel's hair 
pencil for the kaolin plug. This variation of the 
N P electrode is somewhat more difficult to pre- 
pare, but is more convenient for certain uses. 

51 



52 



LABORATORY GUIDE IN PHYSIOLOGY. 



(V) If one has not the zinc rods at hand he may readily 
prepare an efficient N-P electrode as follows: 1st. 
Take 5 cm. of No. 16 copper wire, make one end 
perfectly clean and bright. 2d. Dip the bright end 
into molten c. p. zinc. The zinc adheres to the 
wire, and if the dipping be repeated two or three 
times the lower 1 centimeter of wire will have a 




Fig. 9. 



Fig. 9. Nonparizable electrodes, hand electrode. 

The Du Bois-Reymond, N-P electrodes, shown in the two middle 
cuts, are described in the text VI1I=2 (a), (c). 

The Fleischl brush electrode, mentioned in the text [2 (b)], may be 
prepared by setting the brush in stiff kaolin paste, or if a more perma- 
nent electrode is desired, in plaster of Paris. 

A plaster of Paris pencil, as shown in the lower left hand cut, may 
be used for ordinary work with the constant current. 

The hand electrode shown at the right, is used with an induced 
current. 

thick coating of zinc. 3d. Take a glass tube 10 cm. 
long, and with a 4 mm. lumen, draw it in the 



GENERAL PHYSIOLOGY. 53 

middle to about two-thirds its original diameter, 
cut it into two such as shown in the figure. Before 
assembling the parts, that part of the copper wire 
not covered by zinc, excepting the tip (t) must 
be painted with brunswick black or any varnish, and 
the zinc must be amalgamated. With this electrode, 
as with the preceding, zinc sulphate, kaolin and 
NaCl 0.(5 per cent are used. The part C in these 
electrodes may be held in a clamp. 
d. A double myograph. 
A most efficient, as well as convenient and economical 
double myograph may be arranged for this experiment as 
indicated in Fig. 10. 

It will be noticed that two common muscle levers such 
as are shown in Fig. 13, are used, that these are held in 
position by common clamps and heavy support, that the 
upper myograph is reversed and its lever counterpoised 
by the weight (w), that between the two myographs a small 
wooden block — with a longitudinal hole for the loop of 
thread which holds the muscle — is held by a clamp. 
j. The experiment. 

(1) Curarize a frog. (See Appendix A-5.) 

(2) After the lapse of three hours or more, the sartorius 
muscle may be prepared as described in Lesson X. 

(3) Mount the preparation by passing a loop of coarse 
thread through the hole in the block (b), lift the 
muscle by its tendon of insertion, pass it through the 
loop, draw the loop gently around the middle of the 
muscle and fix by making a single knot around the 
screw (s) of the clamp. The fine hooks which join 
the muscle to the levers may now be passed through 
the tendons, and the proper position of the levers 
effected by an adjustment of the clamps. The non- 
polarizable electrodes may be clamped between two 



54 



LABORATORY GUIDE IN PHYSIOLOGY. 



pieces of cork and held by an extra support. A 
"universal" clamp holder is a most desirable acces- 
sory to this apparatus. 
The electrical apparatus should be set up as shown in 

PI. II., Fig. 4. 
With this arrangement either electrode e or electrode 
e' may be made the anode, the experimenter needing only 
to reverse the commutator bridge to reverse the position 
of anode and kathode. 




Fig. 10. 

Fig. 10. Double myograph. Described in the text 
under VIII=3. 

The recording drum or kymograph should rotate 
rapidly. The recording points of the myograph levers 
should be adjusted so that the point of the upper one 
touches the drum vertically over the point of the lower 
one. Adjust the time marker so that it will indicate the 
time of making and breaking the circuit, i. e., so that it 



GENERAL PHYSIOLOGY. 55 

will record on the drum the time of making stimulus and 
the time of breaking stimulus. The recording point of 
the time marker should, of course, be in the same vertical 
line with the myograph points. The moist tips of the 
N-P electrodes should be so adjusted as to just touch the 
muscle above and below the loops of thread. 

(1) Close the key. If the preparation has been sue 
cessful, the half of the muscle in contact with the 
kathode pole will respond before the other one. 

(2) Break the current. The anode should respond first. 

(3) Reverse direction of current and repeat (1) and (2). 

(4) Vary the strength of current through use of simple 
rheocord and determine whether the results are the 
same for currents of different strength. 

Law I. The make- contraction starts at the kathode and the 

break-contraction starts at the anode, or 

When irritable tissue, muscle, or nerve, is subjected to a 

galvanic current the response to the stimulation begins in 

the region of the kathode on making the current and in 

the region of the anode on breaking the current. 

Would the foregoing observations justify the following 
statements: (1) Kathcdic contractions, or make contrac- 
tions, may be caused by a galvanic current which is too 
weak to cause anodic contractions or break contraction. 
(2) Kathodic or make contractions are stronger than 
anodic or break contractions. 



IX. a. The muscle = nerve preparation, b. Indirect 

mechanical, thermal and chemical stimu= 

lation of the gastrocnemius. 

a. The muscle=nerve preparation. 

/ Appliances. — Frog board and pins ; operating case ; 
glass nerve- hooks , like Fig. 11, A, made as follows: Take 
a 10 cm. piece of glass rod, heat and draw in center to 
about 1^2 mm. diameter; cool, cut in two, heat the 
. points to smooth them and bend the end over to form 
the hook. 




A 



Fig. 11. 



Fig. 11. A. Glass nerve-hook; for description see IX=a=/. B. Gastro- 
cnemius muscle-nerve preparation. For description, see text IX=a=j". 

Simple myograph or muscle lever (See Fig. 13). 
Watch glass with salt crystals. 20 cm. of thick copper 
wire. 
2. Preparation. — Pith a frog and fix to frog board, with 
dorsum up. 

It will be taken for granted that the student is familiar 
with the anatomy of the frog's leg and thigh. The ac- 

56 



GENERAL PHYSIOLOGY. 



57 



companying cuts may serve to refresh the memory. 

(Fig 12) 
j. Operation. — To make a gastrocnemius *' muscle nerve prep 

aration." 

(1) Make, with scissors, a circular cutaneous incision 
around the tarsus, corresponding with the lower end 
of cut B. Make a longitudinal cutaneous incision, 
beginning at the margin of the circular incision where 
it crosses the external aspect of the tarsus, carry it 
along the tibia, along the course of the biceps femo 
ris muscle, over the pyriformis to the posterior end 




Fig. 12. 
Fig. 12. Showing the muscles of the frog's thigh and leg. 



of the urostyle, along the whole extent of the uros- 
tyle. From the posterior end of the urostyle make 
an incision posteriorly and ventrally, for 1 or 2 cm. 
Grasp the free margin of the skin at the point of 
the circular incision and with a quick traction 
toward the head of the frog the skin will be re- 
moved from the whole field of operation. 
(2) Pass a point of the fine scissors under the glisten- 
ing tendon of the biceps femoris where it is inserted 



58 LABOR A TOR Y G U1DE JN PHYS10L0G V. 

into the tibia, taking care not to injure any of the 
neighboring tissues. Sever the tendon. Grasp its 
free end, lift the biceps up, carefully cutting the 
delicate connective tissue which joins it to neigh- 
boring structures; sever its heads. The removal of 
the biceps and a separation of the cleft which the 
biceps occupied reveals three blood vessels and the 
large trunk of the sciatic nerve. Which of the blood 
vessels is the sciatic artery? Which the sciatic 
vein? Which the femoral vein? 

Grasp and lift up the posterior end of the urostyle, 
sever the ilio-coccygeal muscies, remove the urostyle. 

The sciatic plexuses formed by the 7th, 8th and 
9th pairs of spinal nerves will be revealed. 

(4) Pass a glass nerve hook under the sciatic nerve, 
gently lift it up, severing, with the scissors, the con- 
nective tissue. The pyriformis muscle must also 
be divided. The whole length of the sciatic nerve 
may thus be readily dissected out. Care should be 
taken not to stretch, pinch or cut the nerve during 
this process. Lay the nerve upon the gastrocne- 
mius muscle. 

(5) Grasp the triceps femoris muscle, pass a blade of 
the scissors under its tendon; sever, and remove 
the whole mass of muscles anterior to the femur. 
In a similar manner remove the muscles posterior 
to the femur. 

(6) Grasp the tendo achillis, sever low down at X; 
lift up the gastrocnemius, sever the tibia and its 
associated muscles as near to the knee joint as 
possible. 

(7) Sever the femur at the juncture of its middle and 
upper thirds. The finished preparation has the 
characteristics shown in Fig. 11 — B. A segment of 
the vertebral column may or may not be left on. 



GENERAL PHYSIOLOGY. 



59 



The indirect stimulation of the gastrocnemius. 

Observations. — To mount the muscle- nerve preparation in 
the myograph. Fix the femur in the clamp (Fig. 13-c); 
place a piece of filter paper, wet with normal saline solu- 
tion, upon the glass nerve support (s); lay the nerve upon 
the support; make a longitudinal slit in the tendo- 
achillis, pass the hook of the muscle lever through the 
slit and so adjust the height of the clamp as to bring the 
lever into a horizontal position. 




Fig. 13. 

Fig. 13. Simple myograph, with a femur-clamp (c), and a glass 
plate (s) for a nerve rest. 

a. Mechanical Stimulation. — (1) Snip off with scissors the 
central end of the sciatic nerve. If the muscle in- 
stantly contracts, thereby lifting the lever, the ob- 
server will know that his preparation is successful. 
If it does not respond to the first stimulation it may 
to a second or subsequent one. If it responds to 



LABORATORY GUIDE IN PHYSIOLOGY. 

later stimuli but not to the first ones, one may con- 
clude that in making the preparation a portion of 
the central end of the nerve was killed. 
(2) What may one conclude if the muscle responds 
to stimuli applied to the central end of the sciatic 
nerve, but later fails to respond to stimuli applied 
farther along the course of the nerve, i. e., nearer the 
muscle? 

b. Thermal Stimulation. 

(3) Make and mount a fresh preparation. Heat the 
copper wire in a gas flame and touch the end of the 
nerve with the hot wire. If the preparation has 
been successful the muscle will respond by a contrac- 
tion. If the preparation is a good one save at least 
2 /l of the nerve for the subsequent experiment. 

c. Chemical Stimulation. 

(4) Cut off the part of the nerve which is dead and 
lay the central end of the still functional nerve in a 
saturated solution of common salt. Await results. 
Record all results. 



X. Variation in the method of applying mechanical, 
thermal and chemical stimuli. 

/. Appliances. — Operating case; kymograph; myograph; 
3 frogs. 

2. Preparation. — Much interest will be added to these 
experiments if a permanent record be made of the move- 
ments of the lever when the muscle responds to a stim- 
ulus. The most practical method of recording these 
movements is to cause the lever point to trace them upon 
a moving surface. It is customary to use a rotating cyl- 
inder, upon which is fixed a glazed paper which may be 
smoked in a gas flame. The kymograph — wave writer — 
an instrument much used for this purpose, consists of a 
metallic cylinder and a clock work for its propulsion. 
(See Fig. 14.) 

Describe the structure of the kymograph giving fig- 
ures. 

To prepare the kymograph for work. (See Appendix 
A-6.) 

To cur arize a frog. (See Appendix A-5.) 

j. Operation. — To make a sartorius preparation. After the 
frog has come under the influence of the curare, pass a 
blade of the fine scissors under the tendon of insertion 
of the sartorius; cut it as close to the tibia as possible; 
grasp the tendon with forceps and carefully lift it up, 
cutting, with the scissors, the connective tissue which 
holds the muscle in place; follow it as far as possible and 
get as much of the tendon of origin as possible. Mount 
this preparation by tying a thread to each terminal tendon, 
and fixing one thread to the myograph clamp and the 

61 



62 



LABORATORY GUIDE IN PHYSIOLOGY. 



other to the tracing lever. This muscle should not be 
made to lift as heavy a weight as is used for the gastroc 
nemius. 
Observations, 
{a) Direct versus indirect stimulation. 

(1) Put saturated salt solution upon the sartorius — di- 
rect stimulation. If it responds take a tracing of the 
response. 




Fig. 14. 
Fig. 14. The Kymograph. For description see Appendix C. 

(2) Mount the second sartorius and try mechanical 
and thermal stimuli, tracing and recording results. 

(3) Prepare and mount a gastrocnemius preparation, 
from a frog that was not curarized. Apply various 
stimuli to the nerve — indirect stimulation — as in the 
previous lesson and record results. 



GENERAL PHYSIOLOGY. 63 

(&) Qualitative variation of stimuli. — Make and mount a 
gastrocnemius preparation for indirect stimulation. 

(5) Study the response to the following variations of 
mechanical stimuli : cutting, pinching, tapping, 
pricking. 

(6) Study the responses to the following variation of 
thermal stimuli : ice, hot wire. 

(7) How does the muscle respond to indirect stimula- 
tion with glycerine, alcohol ? 

(V) Quantitative variation of stimuli. Use gastroc- 
nemius preparation. 

(8) Mechanical stimuli : light tapping, heavy tapping. 

(9) Thermal stimuli : Touch the nerve with the wire 
which has been held in boiling water, i.e., 100° C. 

Touch the nerve with a wire which has been 
heated to redness in a gas flame. 

(10) Chemical stimuli : Put the end of the nerve into 
0.6 % solution of common salt. Follow this with ^ 
saturated solution of common salt. Compare the 
results with those obtained when a saturated solu- 
tion was used. 

(d) Variation in the length of time of applying stimulus. 
Use gastrocnemius preparation. 

(11) Cut off, or pinch off the nerve very slowly. This 
may be done so slowly and with such a gradual in- 
crease of pressure as to cause no contraction of the 
muscle. 

(12) Put the central end of the sciatic into tepid 
0.6 °] NaCl solution, and gradually bring to a 
boil, protecting the muscle and that part of nerve 
not in the solution, with absorbent cotton moistened 
in normal saline solution. 

The nerve may be functionally destroyed without 
causing a contraction of the muscle. 



64 LABOR A TORY G UIDE IN PHYSIOLOGY. 

(13) Put the central end of the nerve into NaCl 0.6 % 
and gradually add salt to saturation. Take another 
preparation, put the nerve into a few drops of 
NaCl 0.6 %. Add alcohol drop by drop until the 
mixture is about 90 % alcohol. Record results. 



XI. Electricity as a stimulus. The galvanic current. 

i. Appliances. — Operating case; 3, 10 cm. pieces of uncov- 
ered copper wire; a piece of zinc; beaker; a Daniell 
cell; kymograph; myograph; simple contact key; 4 cov- 
ered battery wires; 2 frogs. 

2. Preparation. 

(1) Curarize a frog. 

(2) To prepare a " water element : ," take a small bright 
piece of zinc, wind one end of a 10 cm. piece of cop- 
per wire around it, remove the glass plate from the 
middle clamp of the myograph, clamp twc copper 
wires so that one or two centimeters of wire will ex- 
tend out horizontally on one side of the clamp, while 
the other longer ends extend out on the other side; 
one of these is wound around the piece of zinc. Bend 
these long ends down to the perpendicular. Do not 
allow these wires to touch each other in any part of 
their course. 

(3) Charge the Daniell cell (See Appendix A-4), insur- 
ing the proper amalgamation of the zinc. Do not put 
the zinc into the cup until the cell is to be used. 

j. .Experiments and Observations. 

(1) Take two coins of different metals, preferring cop- 
per and silver. With a knife or file brighten on the 
circumference of each two small surfaces removed 
from each other by J to | the circumference. Touch 
each coin separately to the tongue. Now bring the 
two coins into close contact at bright points, leaving 
the other two fresh surfaces in such a position that 
the tongue may touch both at the same time. Touch 
65 



66 LABORA TOR Y GUIDE IN PH YSIOLOG Y. 

the coins with the tongue as indicated. Is there any 
difference in the sensation which the tongue receives 
in these two experiments ? Record results, account- 
ing for phenomena. 

(2) While in the operation of making a gastrocnemius 
preparation, after the sciatic nerve has been freed from 
the other structures in the thigh, slip the glass nerve- 
hook under it so that the handle of the nerve-hook 
will hold the nerve away from the other tissues. Press 
the end of a copper wire against the muscles of the 
thigh, touch the silver probe to the sciatic nerve, then 
to the copper wire, first separately, then simultane- 
ously. 

Vary the experiment by using other combinations: 
Silver and steel, copper and steel, etc. Note briefly the 
original observations of Galvini. Are the observations 
just made different in any essential respect from the 
observation which led to the discovery of what we call 
galvanic electricity? 

(3) Complete the gastrocnemius preparation, mount the 
muscle in the myograph, place the nerve across the 
horizontal ends of the two wires, lift the beaker of 
water and immerse the two pendant plates — the cop- 
per wire and the piece of zinc. 

If the experiment is successful the muscle responds 
vigorously. Is there any chemical action in this water 
element? If so, describe it. Would oxidized or tar- 
nished plates answer as well as bright ones? 

(4) Mount another gastrocnemius preparation, adjust 
the Daniell cell for action, set up the electric apparatus 
as shown in Plate II, Fig. 5, clamp the two exposed 
poles (p.) in the middle clamp so that the ends are 
exposed for about two centimeters. Place the nerve 
across the poles. Adjust the kymograph for tracing 
a myogram. 



GENERAL PHYSIOLOGY. 6? 

(#) Close the key, i. e. "make" the current, and hold 
the key down for several seconds. Note results 
and take tracing. 

(b.) Open the key, i. e. "Break the current." 
Note results and take tracing. 

(V.) Make and break the current during one rotation 
of the drum. If there is a response on both make 
and break, so time the closing and opening of the 
key that these will come in pairs with a consider- 
able pause between. Before fixing the tracing, 
(see Appendix A-7. ) mark each wave which was 
the effect of making the current m., and each wave 
which was caused by breaking the current, b. 

(5) Prepare and mount a sartorius from the curarized 
frog. Bring the two poles into contact with the 
muscle, and repeat the experiments suggested under 

(*■) 

(6) In experiments (4) and (5) the observer has applied 
electric stimulation of medium strength both directly 
and indirectly to the sartorius and gastrocnemius 
muscles. He is justified in formulating certain con- 
clusions — subject to subsequent modification. 

Formulate conclusions. 

(7) Describe minutely the chemical and physical proc 
esses going on in the active Daniell cell. 



XII. Stimulation with the constant current. The 
simple rheocord. 

/. Appliances. — Operating case, kymograph and myograph; 
3 or 4 Daniell cells; simple rheocord; materials for mak- 
ing nonpolarizable electrodes, (see demonstration 
VIII); Pohl's commutator with cross-bars; Du Bois 
Reymond key; 9 wires; 3 frogs. 

2. Preparation. 

(].) Make a pair of N P electrodes. 

(2.) Set up apparatus as shown in PI. II, Fig. 6. 

j. Operation. — Make and mount a gastrocnemius prep,! 
ration and so adjust the nerve to the electrodes that the 
current will be a "descending" one, i. e. so that the 
kathode will be nearer to the muscle than is the anode 

4. Observations. 

(1) (a) Open the short-circuiting Du Bois-Reymond 
key — i. e. make the long circuit. 

(b) Close the key, thus breaking the long circuit, or 
muscle-circuit. 

(c) Take a tracing of a series of alternating make and 
break shocks with descending current. 

(d) Take a tracing with ascending current. How may 
one change the direction of the current along the 
nerve without changing the adjustment of nerve 
and electrodes ? 

(2) (a) Give the preparation a stronger stimulus by 
joining two cells. Should one join the cells in series 
or multiple arc ? Why ? 

(b) Take a tracing as before using the descending 
current. 

68 



GENERAL PHYSIOLOGY. 



69 



(c) Vary the experiment by the use of the ascending 
current. 

(3) (a) Increase further the strength of the stimulus by 
the use of a battery of three or four cells. 

Record effect of descending current, 
(b) Record effect of ascending current. 

(4) Set up electrical apparatus with simple rheocord as 
shown in PI. II. Fig. 1. Instead of making a tracing 
tabulate the results. 

(a) Adjust for stimulation with the minimum descend- 
ing current. Make the muscle circuit and record 
whether the muscle contracted, or remained at rest. 

(b) Stimulate with minimum ascending current and 
record. 

(c) Gradually strengthen the current, recording at 
each position of the slider the results for both de- 
scending and ascending currents, make and break. 

The following form of table should be used: 



STRENGTH 

OF 
CURRENT. 


DESCENDING. 

Make. 1 Break. 


ASCENDING. 

Make. [ Break. 


Weak. 

Medium. 

Strong 


Contract.; Rest. 










1" 



(5) Sum up the day's work in a series of conclusions. 



XIII. The effect of the induced current. 

/. Appliances. — Operating case; inductorium with Neef 
hammer; contact key; DuBois Reymond key; 1 wires; 
1 Daniell cell; materials for making hand electrodes [2 
No. 24 or 28 wires }4 meter long, 2 pieces of capillary 
rubber tubing 4 or 5 cm. long, thread]; 2 frogs. 
2. Preparation. — (a) To make hand electrodes for use with 
induced currents. Push a thin wire through a piece of 
capillary rubber tubing (capillary glass tubing may be 
used instead of the rubber), bring two such side by side 
and wrap thread around them. If glass tubing be used 
the wire will need to be fixed in the tubes with a drop of 
sealing wax. 

Such a pair of hand electrodes are shown in Figure 9> 
page 52. 

(fi) Set up electric apparatus with contact key in 
primary circuit and short-circuiting key in secondary 
circuit. 
j. Operation. — Make and mount gastrocnemius prepara- 
tion. 
4. Observations. 

(1) Take tracings of the contractions produced by a 
series of " make, induction shocks " applied indirectly. 
The " make, induction shock" is obtained as follows: 
(a) With primary circuit not interrupted by the 
Neef hammer, but closed and opened only by the 
contact key; open the short-circuiting key of the in- 
duced circuit. 

(£) Close the contact key of the primary circuit, a 
make induction shock — i. e., a shock in the in- 
70 



GENERAL PHYSIOLOGY. 71 

duced circuit caused by a closure of the battery- 
circuit — will stimulate the preparation. 

(V) Close the short-circuiting key in the secondary 
circuit. 

(d) Open or break the primary circuit. An induced 
break shock occurs in the secondary circuit but it 
is short-circuited by the closed Du Bois Reymond 
key. If while the drum rotates one makes, in 
close succession, the changes above indicated — 
a-b-c-d-a-b-c-d etc. — there will be produced a 
series of contractions, all the result of stimulation 
by make induction shocks. 

(2) Take a tracing of the contractions resulting from 
a series of indirectly applied break induction shocks. 

(3) By leaving the short-circuiting key open, one may 
get a series of contractions due to alternating make 
and break induction shocks. Let these be re- 
corded in pairs upon the kymograph. 

(4) Determine the distance which the secondary coil 
may be removed from the primary coil and get any 
response to the make or break. Which is more 
effective make or break ? Can one find a position 
of the secondary coil where there are only make or 
break shocks? What are the limits of this position ? 
Within the limits of that position where both make 
and break contractions occur are there differences 
in the height of the make or break waves? Is there 
a position of maximum height for both waves ? If 
not, is there a position of maximum height for each 
wave? 

Make a tracing on a slowly rotating drum, while 
gradually moving the secondary coil from the great- 
est distance which gives a contraction up to the 
zero point. Record at intervals upon the tracing 



72 LABORATORY GUIDE IN PHYSIOLOGY. 

the positions of the secondary coil at that point in 
the tracing. 

(5) Still leaving the short-circuiting key open make 
and break the primary current as rapidly as it is pos- 
sible to close and open the key in the primary circuit. 
Take tracing. 

(6) So adjust the apparatus that the Neef hammer is 
brought into the primary circuit, thereby making 
and breaking that circuit with each vibration of the 
hammer. Mount a fresh gastrocnemius, adjust the 
kymograph for slow or medium rotation. 

Close the short circuiting key; close the key in 
the primary circuit. The Neef hammer should start 
to vibrating and continue to do so as long as the 
primary circuit is closed. Start the kymograph. 
After an abscissa a few centimeters in length has 
been traced upon the drum, open the short-cir- 
cuiting key. If the experiment is successful the 
muscle willbe tetanized. Allow the tetanizing cur- 
rent to operate until a tetanus tracing several centi- 
meters in length has been traced. Close the short- 
circuiting key. 

After a few moments the muscle may be again 
tetanized, and repeatedly so until exhausted. 



XIV. The work done by a muscle, a. To determine the 

amount of work done by a single contraction. 

b. To determine the total amount of work 

done by a muscle, c. Reaction 

changes in fatigued muscle. 

/. Appliances. — Same as in lesson XIII.; also 50-gramme 
weight and 20 or 30-gramme weight. 

2. Preparation. — Arrange electrical apparatus for a series 
of break induction shocks. 

?. Operation. — Make and mount a gastrocnemius prepara- 
tion for indirect stimulation. 

4.. Observations. — Upon a slow drum record in close order a 
series of break contractions. 

a. To determine the amount of work done by a single 

contraction. 

(1) What weight is lifted? 

(2) How high is it raised? 

(3) What is the ratio between the height of the curve 
traced by the lever and the height through which 
the weight was raised? 

(4) Let W = work done. 

g = weight lifted. 

h = height of curve traced by lever. 

&— constant of the apparatus, in this case 

the ratio between the lever arms. Then 

W=«. g. h. 

(5) Express the amount of work in ergs. 

b. To determine total work done. 

(5) How many times was the weight lifted before the 
muscle was fatigued? 
73 



74 LAB OR A TOR V G WDE IN PH YSIOL OGY. 

(6) Through what average height was the weight 
lifted ? 

(7) Has the value of k or g changed? 

(8) Give a formula for total height (H = ). 

(9) Give a formula for total work done (W = ). 

(10) Express in ergs, the total work done by the muscle. 

(11) In the fatigue tracing did the lever continue 
throughout the observation to fall back to the orig- 
inal abscissa ? If not, describe any general changes 
in the abscissa. 

c. Reaction changes. 

(12) Apply a piece of neutral litmus paper toj the 
fresh muscle tissue of the frog from which your 
specimen was taken. Record result. 

(13) Apply a piece of litmus paper to a fresh cut sur- 
face of the fatigued muscle. Record results. 

(14) What is the reaction of the muscle of a frog 
after rigor mortis has been established? 

(15) What is the reaction of fresh urine? 



XV. Demonstration: Electrotonus; to determine the effect 
of a constant current upon the irritability of a nerve. 

At the beginning of this century Ritter discovered that 
the vital properties of irritable and contractile tissues 
were modified when subjected to a constant battery cur- 
rent. This modified condition was called galvanismus. 
During the first half of this century the subject was in- 
vestigated by Nobili, Mattencci, Valentin and Du Bois- 
Reymond ; the last named substituted the word electro- 
tonus for galvanismus and further modified the terminology. 
It remained for Pfliiger (Untersuchungen iiber die Physio- 
logie des Electrotonus, Berlin, 1859) to rework the whole 
field, to correct, to elaborate, and finally to formulate laws. 
a. Preliminary experiment. 
i. Appliances. — Muscle- signal ; 2 Du Bois-Reymond keys; 

2 Daniell cells ; commutator ; 8 wires ; salt. 
2. Preparation.— Set up electrical apparatus as shown in 

PI. II. Fig. 8. 
j. Operation. — Make and mount in the muscle signal a 

gastrocnemius preparation. 
4. Observations. 

(1) In which position must the bridge of the commuta- 
tor stand to give a descending current? Mark that 
side of the commutator D. Mark the opposite side A. 

(2) With a descending current, which pole is the 
kathode, a or b ? 

(3) PI. II. Fig. 8-p represents the glass plate of the 
muscle signal. So arrange the triangular platinum 
electrodes that there shall be a distance of about 1 
cm. between the electrodes, and both electrodes near 

75 



7 6 LABOR A TOR Y G U1D E IN PH YSIOL O G Y. 

that end of the plate farthest from the muscle. Lay 
the nerve over the electrodes and along the glass 
plate. The segment of nerve which lies upon the 
glass plate between the electrodes and the muscle 
may be subjected to various stimuli, mechanical and 
chemical. Sterling (Prac. Phys., p. 244) uses salt. 
At a point about 1 cm. from the electrodes, marked x 
in the figure, place upon the nerve trunk as many fine 
crystals of common salt as would be taken up on the 
point of a penknife. Moisten these salt crystals with 
a drop of water. While the salt solution is per- 
meating the sheath of the nerve trunk, adjust the com- 
mutator for a descending current. When the muscle 
begins to twitch, note the effect upon the signal. The 
contractions become more and more tetanic in 
character. 

(4) Close the commutator circuit, open the short-cir- 
cuiting key, i. e., make the "polarizing" current. If 
the experiment is successful the tetanus is more 
marked. Which pole is nearer the point stimulated? 

(5) Close the short circuiting key, i. e., break the 
" polarizing " current. Reverse the commutator; 
make the current. The muscle is put completely or 
almost completely at rest. Which pole is nearer the 
stimulus? 

(6) Repeat (4) and (5) several times. It is evident 
that the irritability of the nerve to the salt stimulus is 
increased in the region of the kathode, and decreased 
in the region of the anode pole. This changed con- 
dition of the nerve due to the passage of a constant 
current is called electrotonus. The state of increased 
irritability in the region of the kathode is called 
katelectrotonus. The decreased irritability in the region 
of the anode is called anelectrotonus. 



GENERAL PHYSIOLOGY. 77 

b. Myographic record of anelectrotonus and of katelectrotonus. 
i. Appliances. — 3 or 4 Daniell cells; 3 Du Bois- 
Reymond keys; contact key; 2 commutators; induc- 
tcrium; 2 N-P electrodes; 18 wires; kymograph; 
myograph with moist chamber; 2 pairs of platinum 
wire electrodes to use with induction currrent. 
2. Preparation. — Arrange apparatus according to plan 
shown in PL II., Fig. 9. Note that the cross bars 
are absent from the commutator in the induction cir- 
cuit. This enables one to stimulate the nerve at the 
central end (c) or at the segment between the polar- 
izing electrodes and the muscle (m), by simply revers- 
ing the bridge of the commutator (B). 
j. Operation. — Make and mount a gastrocnemius prepa 
ration in moist chamber myograph; adjust drum for 
tracing myogram. Adjust electrodes as shown in 
diagram. 

Test apparatus and preparation by sending single 
make (or break) induction shocks through nerve at c 
or at m. Let there be a typical response at both 
places. The secondary coil should be removed to a 
distance that gives a little more than the minimum 
stimulus required to cause a contraction of the muscle. 

To close the constant current "polarizes" the nerve 
or, better, induces electrotonus. 

That segment of the nerve between the anode and 
kathode is called the intrapolar region. 

Those segments centrally and distally located are 
called extra polar. 

The induced current is called the stimulating cur- 
rent. 
4. Observations . 

(1) Adjust for descending, polarizing current. Stimulate 
at c, i. e. in the region of anode. Note — trace — ex- 



78 LAB OR A TOR V G UIDE IN PH YSIOL OGY. 

tent of muscle contraction. Induce electrotonus, 
stimulate again in region of anode. If the experiment 
is successful the contraction will be found to be de- 
creased or absent. 

The nerve is, at the point c, in a condition or anelec- 
trotonus [descending extra polar anelectrotonus]. 

(2) Stimulate at m, or in the region of the kathode. 
Withdraw polarizing current. After a few minutes 
stimulate again at m. If the experiment is successful 
the wave is higher in the former than in the latter 
case. 

The stimulation was made in the region of the 
kathode and the nerve in a condition of kathelectrotonus. 
[Descending extrapolar kathelectrotonus] 

(3) Adjust for ascending, polarizing current. 
Stimulate at m, i. e., in the region of the anode. The 

contraction is weaker than in the normal nerve, or it 
may be quite absent. This region is now in a condi- 
tion of anelectrotonus. [Ascending extrapolar anelec 
trotonus.] 

(4) Stimulate in the region of the kathode. The re- 
sponse is probably weak. Withdraw the polarizing 
current. Stimulate again in the region of the kathode. 
The response is normal, i. e., it is greater than during 
the electrotonic condition. 

But in descending extrapolar kathelectrotonus the re- 
sponse was greater than normal. In the experiment 
just performed we stimulated in the region of ascend- 
ing extrapolar kathelectrotonus. Note that the polariz- 
ing current is relatively strong. 

(5) Remove one cell from the battery and repeat (4.) 
If the response to stimulation is still weaker with than 
without the polarizing current, reduce the strength of 
the polarizing current still farther by use of the simple 



GENERAL PHYSIOLOGY. 79 

rheocord. Finally with a weak polarizing current, the 
stimulus in the region of ascending extrapolar kathe- 
lectrotonus causes a stronger response than normal. 

The response which the muscle makes must be 
accepted as a measure of the excitation which 
it receives from the nerve. But the excitation 
delivered by the nerve depends upon two factors, its 
irritability and its conductivity. When the nerve is 
stimulated in the region of ascending extra or intra- 
polar kathelectrotonus, its increased irritability is of 
no avail if there is interposed between that region 
and the muscle a region of decreased conductivity. 
With strong polarizing currents the region of the 
anode is not only decreased in irritability but also in 
conductivity. 
Laws of electrotonus. 

I. The passage of a constant current through a nerve in- 
duces a condition of electrotonus marked by an increased 
irritability in the region of the kathode (kathelec trot onus) 
and a decreased irritability in the region of the anode 
(anelectro tonus) . 

II. During electrotonus induced by a strong current the con- 
ductivity is decreased in the region of the anode. Further 
— though not derived from the foregoing experiment — " at 
the instant that the polarizing current is withdrawn the 
conducting power is suddenly restored in the region of 
the anode and greatly lessened or lost in the region of 
the kathode." — Lombard, in American text- book of 
Physiology. 



XVI. Demonstration: Pfluger's law of contraction. 

Appliances. — Du Bois-Reymond rheocord, or simple 
rheocord; 3 Daniel cells; muscle signal or myograph 
with moist chamber; 2 Du Bois-Reymond keys; com- 
mutator; 2 N. -P. electrodes. 

Preparation. — Set up the apparatus with three cells in 
series, Du B.-R. key as closing key. Commutator with 
cross-bars, Du B. R. rheocord in short circuit, short-cir 
cuiting key, the two N P. electrodes clamped in cham- 
ber of myograph. 

Operation. — Make and mount a gastrocnemius prepara- 
tion. 

Observations. 

(1) Stimulate with make and break of the weakest pos- 
sible descending current. 

Record results in such a table as that suggested in 
laboratory, lesson XII. 

This table shows what response (contraction or 
rest) the muscle gives on the making and breaking of 
the descending current and on the making and break- 
ing of the ascending current. 

It also shows in a marginal column the gradual in- 
crease of the strength of the current through gradual 
increase of resistance in the short-circuiting rheocord. 

(2) Make and break with weak ascending current. If 
the conditions are typical the muscle will contract on 
making both ascending and descending current. 

(3) Increase gradually the strength of the electrode cir- 
cuit, recording results. After a longer or shorter 
transitional period in which the result will be varied 

80 



GENERAL PHYSIOLOGY. 



81 



by a contraction on both the make and break of the 
ascending current, one comes to a strength of current 
which causes a contraction on both make and break 
of both descending and ascending current. This is 
the medium strength for the preparation and the con- 
dition in question. 

(4) Let the current be increased still further and by 
larger increments. After passing another transitional 
stage one finally reaches a strength of current which 
causes a contraction on make of descending current 
and break of ascending current. This is the strong 
current for the preparation under observation. 

It not infrequently happens that through overstim- 
ulation and fatigue of muscle the whole experiment 
cannot be completed upon one preparation except by 
increasing the current by larger increments. 

(5) Pfliiger's law of contraction may be expressed in the 
following table: 



STRENGTH 

OF 
CURRENT. 


DESCENDING. 


ASCENDING. 


Make. 


Break. 


Make. 


Break. 


Weak. 


C 


R 


C 


R 


Medium. 


C 


C 


C 


C 


Strong. 


c 


R 


R 


C 



(6) But how shall we account for these results? 

Let us recall some of the laws which have been dem- 
onstrated. 
Law I. The influence of make and break stimulation. 
The make contraction starts at the kathode and the break 
contraction starts at the anode. Further, kathodic or make 
co?itractions may be caused by a current which is too weak to 
cause anodic or break contractions. 



82 LABORATORY GUIDE IN PHYSIOLOGY. 

Law II. A law of Electrotonus. 

The passage of a constant current through a nerve induces a 
condition of electrotonus, marked by an increased irritability 
in the region of the kathode, and a decreased irritability in 
the region of the anode. 

Law III. A law of Electrotonus. 

During electrotonus induced by a strong current the con- 
ductivity is decreased in the region of the anode. 

With the help of these laws account for all the typical 
phenomena observed above. 



PART II. 



SPECIAL PHYSIOLOGY. 



S) 



C. CIRCULATION. 



XVII. The circulation and its ultimate cause, a. To 

observe the capillary circulation, b. To observe 

the action of the frog's heart. 

a. To observe the capillary circulation. 

i. Appliances. — Cork board 8 cm. wide by 20 cm. long and 
about y^ cm. thick; cover glasses, 18 mm. in diameter 
and 10 mm. in diameter; normal salt solution; camel's 
hair brush ; pins ; compound microscope ; sealing wax ; 
thread ; filter paper ; 2 per cent croton oil in olive oil. 

2. Preparation. 

Pith two frogs the day before the observation is to be 
made. At the beginning of the laboratory period when 
the observation is to be made curarize the frog lightly by 
the hypodermic injection of one drop of a 1 per cent 
solution of curare. Make a frog-board by cutting a hole 
1.5 cm. in diameter near one corner of the cork board 
and fasten a large cover glass over the hole with sealing 
wax. 

j. Operation. — After the frog becomes curarized, pin it out 
ventral surface downward in such a way as to bring one 
of the hind feet over the hole in the board. Tie thread, 
not too tightly, to the third and fourth digits, loop the 
threads over pins and gently separate the digits until the 
web is quite flat and closely approximated to the surface 

85 



86 LAB OR A TOR Y G UWE IN PHYSIOLOG Y. 

of the fixed glass which covers the hole. Run a film of 
normal salt solution under the web ; place a drop of the 
same liquid upon the upper surface of the web ; place a 
small cover glass over it; fix the board upon the micro- 
scope stage so as to admit of illumination by transmit- 
ted light; illuminate; focus under low power. 
4.. Observations. 

(1) Observe the movement of corpuscles within blood 
vessels of varying size and irregular course. Make a 
drawing of the field of observation showing the rela- 
tive size, the course and anastomoses of the blood 
vessels. 

(2) Observe whether the motion is equally rapid in all 
vessels ; if not, observe whether the slower currents 
are in the larger or the smaller channels. Determine 
which of the vessels are arterioles, which capillaries, 
and which venules. 

(3) Have you seen evidence of intermittent force acting 
upon the corpuscles? If so, desciibe its influence. 
Determine whether this intermittent force makes 
itself evident in all of the vessels ; if not, in which 
class of vessels is it present? 

(4) Do the corpuscles change shape? If so, under 
what circumstances? 

(5) Remove the cover glass, dry the web with filter 
paper, touch a point with a pin that has been dipped 
into dilute croton oil. Without replacing the cover 
above the web observe whether the presence of the 
croton oil effects any change in the diameter of the 
vessels, or in the rate of the blood flow. If there is a 
change in both, has one a causative relation to the 
other ? 

(6) Note and describe minutely all changes which take 
place at and near the place touched with the croton 



CIRCULATION. 87 

oil. If no marked change is produced by the croton 
oil, touch the point with a needle which has been 
dipped into strong nitric acid. 
(7) Observe with a high power. Have you noted di- 
apedesis of white or of red corpuscles. If so, describe 
the process minutely. 

b. To observe the action of the frog's heart. 

/. Appliances. — Dissecting board; fine scissors; heavy 
scissors; pins; forceps; watch glass; camel's hair brush; 
normal salt solution; fine silk thread; ice, in a beaker. 

2. Preparation. — -Pith a frog, lay it with its dorsal surface 
upon the dissecting boaid; stretch out its legs and pin 
the feet to the board. 

j. Operation — Make a median incision through the skin 
from the pelvis to the mandible; make transverse inci- 
sions and pin out the flaps. Raise the tip of the epi- 
sternum; insert a blade of the fine scissors under it and 
divide it transversely, about y? cm. anterior to the tip. 
Raise the anterior segment of the sternum at the point 
of the transverse incision; insert the blade of the strong 
scissors under it and divide it longitudinally in the 
median line. Withdraw from the board the pins which 
fix the anterior extremities, make gentle, lateral traction 
upon the fore feet until the split sternum is sufficiently 
separated to afford a convenient working distance and 
to plainly expose the whole heart. 

4. Observations. 

(1) Note rate of systole. 

(2) Note sequence of contraction of auricles, ventricle 
and bulbus. 

(3) Note change in shape of different parts. 

(4) Note change in color and the position of the same 
in the heart-cycle. 



88 LABOR A TOR Y G UIDE IN PHYSIOL OGY. 

(5) Carefully excise the heart including the sinus veno- 
sus and the bases of the posterior and two anterior 
venae cavae, also the bases of the two aortic trunks. 
Place the excised heart in a watch glass. Observe 
whether the pulsation continues. If so, what is your 
conclusion regarding the relation of the heart move- 
ments to the central nervous system? 

(6) If the pulsation continues, note whether the rate 
of pulsation has been noticeably changed by the ex- 
cision. 

(7) Bathe the heart with a few drops of normal solution. 
Hold the watch glass in the palm of the hand and note 
whether the rate changes. 

(8) Float the watch glass upon ice water and note the 
results. 

(9) If the heart seems vigorous (otherwise procure a 
fresh one), carefully sever the sinus venosus with the 
fine scissors. Does the sinus continue to beat ? Does 
the heart continue to beat ? Interpretation. 

(10) If the heart beats, sever the auricle from the ven- 
tricle through the auriculo-ventricular groove. Note 
results. 

(11) If the auricles beat, divide them. If they con- 
tinue to beat, do they follow the same rhythm? 

(12) If the ventricle becomes quiescent, stimulate it 
either mechanically or with a single induction shock. 
How does it respond to a single stimulus? Continue 
to subdivide the heart until the parts refuse to respond 
to stimuli. 

(13) Repeat the experiment and see if the same results 
are reached on subsequent trials. Note results and 
give your interpretation. 



XVIII. The graphic record of the frog's heart=beat. 

/. Appliances. — Frog board; a straw or strip of bamboo 20 
cm. long; a cork about 2 cm. in diameter and height; 
pins; needles; sealing wax; parchment paper; a kymo- 
graph, stand and lamp; a chronograph. (See Appendix 
A- 15.) 

2. Preparation. — Use a pithed or a curarized frog. Make a 
heart lever after the model shown by the demonstrator. 

j. Operation. — Open the abdomen of the frog as described 
under XVII-b 3 and expose the heart. Open the peri- 
cardium, place some resistant object — a cover slip for 
instance — under the ventricle. So adjust the heart 
lever that the cork foot of the long arm of the lever will 
rest upon the juncture of the auricles and ventricle. If 
the weight of the lever seems to be too great for the heart to 
move easily, the long arm may be made relatively lighter 
by placing a counterpoise upon the short arm. If the 
tracing point of the long arm has a sufficient excursion 
to make a good tracing, bring the kymograph to a posi- 
tion where the point will lightly touch the carboned 
surface of the drum. The lever should be nearly tan- 
gent to the surface of the drum, and so arranged that 
the rotating surface of the drum turns away from the 
tracing point of the lever rather than toward it. 

4. Observations. 

(1) Note whether the curve is a simpie one or com- 
posed of a major wave, with crests superimposed 
upon it. 

(2) In either case closely observe the phases of the 
heart-cycle and determine the relation of each part 

89 



90 LA BORA TOR Y G UIDE IN PHYSIOL OGY. 

of the cycle with each part of the tracing. If the 
tracing has a single crest, more delicately counterpoise 
the lever and more carefully adjust the narrow foot of 
the lever to the auriculo-ventricular groove and repeat 
the experiment. 

(3) Take tracings of the auricle alone. Compare these 
with those of the auriculo-ventricular groove and deter- 
mine the causes of the variation. 

(4) Without altering the counterpoise take a tracing of 
the ventricle and compare it with the two preceding 
curves and account for all the differences. 

(5) Try to take a double tracing with one lever foot 
resting upon the auricle and the foot of the second 
lever resting upon the ventricle. The tracing points 
must touch the drum in a vertical line. Are the 
crests synchronous? If not, why? 

(6) If a time tracing be added by means of the chrono 
graph one may determine the time relations of the 
different phases of the heart cycle. 



XIX. The apex=beat. The heart=sounds. 

i. Appliances. — A cardiograph and a transmitting tambour 
(Marey) or materials for constructing them. A stetho- 
scope; a stand and support; clamps; a kymograph; two 
tambour pans Nos. 1 and 2; thin sheets of rubber; thread; 
corks; sealing wax; tambour holder; straws; needles; 
parchment paper; chronograph. 
2. Preparation. — With the materials furnished by the dem- 
onstrator construct a cardiograph and a recording tam- 
bour, [Appendix A., Nos. 8-9.]. Join the tube of the 
cardiograph to the tube of the recording tambour with 
a rather thick-walled rubber tube 50 centimeters in 
length. Fix the recording tambour with clamp and 
support, and bring it into adjustment for tracing the 
cardiogram upon the kymograph. Adjust chronograph, 
j. Operation. — Let a student remove the clothing from the 
region of the apex beat of the heart and take, upon the 
table, a recumbent dorso-sinistral position. In some 
cases, however, better results are obtained if the sub- 
. ject sits beside the table. Place the button of the 
receiving tambour upon that point of the thorax most 
affected by the apex beat of the heart. The move- 
ments of the chest wall will be faithfully transmitted 
and magnified by the two tambours. 
4.. Observations. 

(1) Note the exact point upon the chest where the apex- 
beat is most distinctly marked. Is it the same for 
different members of the class? 

In recording the location of the apex- beat use the 
bony landmarks of the chest rather than the nipple. 

91 



92 LABORATORY GUIDE IN PHYSIOLOGY. 

In what intercostal space is it located ? How far to 
the left of the median line of the sternum? 

(2) Take several cardiograms from the same individual, 
being careful so to adjust the apparatus as to gain the 
maximum excursion of the lever. What features have 
all of these tracings in common ? What features seem 
to be accidental and nonessential? What are the causes 
of the essential features? What are the sources of the 
nonessential features? 

(3) Take cardiograms of several individuals. Do all of 
them possess the features which seemed essential in 
the first series, taken from one individual ? If not, how 
would you account for the difference? 

(4) With a stethoscope, whose construction you have 
carefully described in your notes, listen to the heart- 
sounds while the cardiograph is tracing the record of 
the heart-movements. Note that two sounds are audi- 
ble and that there is a noticeable pause following the 
shorter, sharper sound; let us call the sound which 
succeeds the pause the first sound. 

(5) With what part of the cardiogram does the first 
sound seem to correspond? With what part of the 
cardiogram does the second sound seem to correspond? 
Give reasons for this correspondence. 

(6) As far as the data will admit, enumerate causes for 
the first sound; for the second sound; for the essen- 
tial features of the cardiogram. 



XX. The flow of liquids through tubes, 
pressure. 



Lateral 



Appliances. — Reservoir with short discharge nozzle 
whose lumen is 6 mm. in diameter; 5 pieces of glass 
tubing whose lumen is about 6 mm. in diameter and 
whose length is 60 cm. ; two lengths of glass tubing 
whose lumen is about 3 mm. in diameter and whose 
length is 60 cm ; rubber tubing for joining up the ap- 
paratus; 3 T tubes of 6 mm. tubing; short tube with 
capillary point from each size of tubing; 2 one liter 
flasks; 2 supports; a light pine stick about 6 feet long; 
compressors (Mohr's). 

Preparation. — A resourceful demonstrator will have no 
difficulty in contriving reservoirs. It is sometimes not 
easy to provide a large class with suitable and conven- 
ient reservoirs. The following form 
has proven very satisfactory: A glass 
tube about 3 cm. in diameter may be 
readily furnished with a glass nozzle of 
the required size by any glass blower. 
The nozzle should be about 3 cm. from 
one end of the tube. That end may 
be closed with plaster of Paris and 
filled with hard paraffin to the lower 
margin of the nozzle-opening. This 
reservoir may be held upright by a 
support. When complete it presents 
the appearance indicated in the accom- 
Fig. 15 panying figure. 



64 cm 




04 LABORATORY GUIDE IN PHYSIOLOGY. 

j. Operation. — Mark upon the side of the reservoir a point 
36 cm. above the center of the nozzle, also a point 64 
cm. above the nozzle. While the reservoir is filled from 
one flask the water may be caught in the other. As- 
sume some convenient unit of time, as 10 or 15 seconds. 
^. Observations. — (a) Fill the reservoir to the height of 64 
cm. 
Allow the water to flow from the nozzle freely into the 
flasks. Observe the force with which the jet issues 
from the nozzle when the water begins to flow. Note 
the difference when the water in the reservoir reaches 
the 36 cm. mark; the 16 cm. mark. What are your 
conclusions ? 

(b) Velocity. — How does the velocity of the discharge 
vary with the varying height of the column of water ? 
Why does it so vary ? Does it verify the law of 
Torricelli? The rate at which a fluid is discharged 
through an orifice [better a nozzle] in a reservoir is 
equal to the velocity which would be acquired by a body 
falling freely through a height equal to the distance be- 
tween the orifice and the surface of the fluid. 

Recall the law of falling bodies. How far will a 
body fall in vacuo, the first, second and third seconds 
respectively? What is the constant acceleration 
per second, due to gravitation ? What is the 
velocity at the end of the first, second and third 
seconds respectively? What is the total distance 
traversed at the end of the first, second and third 
seconds respectively? Let g equal the constant 
acceleration (approximately 32 ft. or 981 cm). Let 
h equal the total distance in centimeters, v the 
velocity and t the time in seconds. Derive from 
the facts the following equations: 
(1) v=gt. 
CO h = ^ 



CIRCULA TION. 95 

From these equations derive: 

(3) v=,y/2gh; (approximately = 4 4.3\/h). 
Expressed as a variation the constant may be dis- 
carded and the variable would read : 

(4) voo^h, or V : v :: VH : tjh. 

Verify the truth of this mathematically derived law. 

(V) Discharge. — The discharge of liquid flowing 
through an orifice must equal the product of the 
area of the orifice and the velocity with which the 
liquid flows. Let D equal the quantity of liquid 
discharged from the nozzle in a unit of time, and r 
equal the radius of the lumen of the discharging 
tube or orifice. Derive the formulae: 

(5) D = 4 4.37rryh. 

(6) D xryh. 

Where one has to deal with two variables he may 
make one of them constant and verify for the other. 
When r is constant: 

(7) D xy/h, or D : d :: VH : Vh- 
When the height is constant: 

(8) D xr 2 , or D : d :: R 2 : r 2 

Verify by experiment formula (7) as follows: 

During a unit of time allow the water to flow from the 

6 mm. nozzle, meantime maintaining a fixed level — 

e. g., at 64 cm. — by pouring water into the reservoir 

from a flask. Note the amount of discharge (D). 

Make the observation also for the 36 cm. height. 

Verify formula (8) by determining D when the 

height is kept constant (64 cm.) and the radius of 

the discharge tube alone is varied. Use, for example. 

a 3 mm. nozzle. But there is another variable not 

considered above, namely, the resistance. 

(d) The relation of discharge to resistance. — Attach to 

the nozzle one length of 6 mm. tubing. Note the 



96 LABOR A TOR V G UIDE IN PHYSIO LOG V. 

discharge in the unit of time. Attach a second 
length of the 6 mm. tubing, taking care that the 
tubing is approximately horizontal. Note the dis- 
charge in a unit of time. What is your conclusion? 
Why does the discharge decrease when the length 
is increased? 

If R equals resistance and L length of tubing, 
does the following expression represent the facts: 

(9) RooL? 

Is the relation of discharge to resistance direct or 
reciprocal ? 

Verify the following formula: 

(10) Dooi- 

We have already found the formula D oor 2 ^h. 
Verify the formula: 

(11) Doo^- h 

(<?) Pressure. — Disjoin all tubes from the reservoir. 
Join a T-tube to the nozzle in this position _L; join 
a segment of large glass tubing to the perpendic- 
ular arm of the T-tube and support it in an upright 
position. 

(1) Fill the reservoir to the 36 cm. mark, allow 
the water to escape from the distal end of the 
T-tube during a unit of time, meantime main- 
taining the height of the water in the reservoir. 
Carefully note the height at which the water 
stands in the upright tube — the piezometer. 

(2) Repeat with water maintained at 64 cm. 
height in the reservoir. 

(3) Join a length of large tubing to the distal 
end of the T-tube; repeat the experiment using 
only the 64 cm. height. 

(4) Join a T-tube with piezometer No. 2, to the 
distal end of the segment of tubing just added 



CIRCULATION. 97 

and repeat the experiment. (Note: The 
piezometers may be held in position by using 
the two supports and the pine stick.) Does 
the addition of the last T tube make any essen- 
tial change in the height at which the water 
stands in piezometer No. 1? Does the reading 
of piezometer No. 2 agree with the reading of 
piezometer No. 1 in experiment (2). 

(5) Add a second segment of large tubing. Re- 
peat the experiment. Does reading of pie- 
zometer No. 2 correspond with reading of pie- 
zometer No. 1 in experiment (3)? 

(6) Add piezometer No. 3. Repeat the experi- 
ment. Does reading of piezometer No. 3 cor- 
respond with that of No. 2 in experiment (4) 
and with No. 1 in experiment (2)? Does read- 
ing of piezometer No. 2 correspond with that 
of No. 1 in experiment (4). 

(7) Attach a large capillary, repeat observations. 

(8) Attach a fine capillary and repeat observa- 
tions. What is the relation of pressure to 
height of column? Does pressure vary as 
height or as the square root of height? 

(9) (a) What is the relation of pressure to the 
central resistance (Re)?/, e., the resistance be- 
tween the point of observation and the reservoir. 

(£) What is the relation of pressure to distal resist- 
ance (Rd)? /. e., the resistance between the 
point of observation and the point of discharge. 

(<:) Which if either of the following formulae repre- 
sents the facts: 
(11 ) P doRc. 
(11') PxRd. 



XXI. a. The flow of liquids through tubes, under the 

influence of intermittent pressure. 

b. The impulse wave. 

a. The influence of intermittent pressure. 

1. Appliances. — Two glass tubes of about 6 mm. lumen and 
about 75 mm. long; a thin elastic tube — thin walled 
black rubber — of about the same lumen as the glass tube 
and about 150 cm. long; a double valved strong rubber 
bulb (about 7.5 cm. long); elastic tubing, large size; 
very thick walled rubber tubing for joining up the appa- 
ratus; Y tube; two flasks, or water receptacles; heavy 
linen thread; a wide capillary and a fine capillary or 
a piece of glass tubing 10 cm. long for constructing the 
same; 500 c. c. graduated cylinder. 

2. Preparation. — Join the large elastic tube to the entrance 
valve of the bulb. Couple the two glass tubes closely 
and join one end to the exit valve of the bulb. Make 
all joints as close as possible and tie tightly with thread. 
Draw a coarse and a fine capillary tube from the 10 cm. 
piece of glass tubing. 

j. Operation. — Clasp the bulb in the hand and make rhyth- 
matical contractions at the rate of about fifteen in ten 
seconds. The process will, of course, pump the water 
from one flask into the other. 
4. Observations. 
a. Intermittent force and inelastic tubes. 

(1) Does the stream of water which is ejected from 
the exit tube flow in a constant or in an intermit- 
tent jet? 

98 



CIRCULATION. 99 

(2) Attach a wide capillary and repeat. What is the 
character of the stream? 

(3) Attach a fine capillary and repeat. Note the 
results. 

b. Intermittent force and elastic tubes. 

(4) Disjoin the glass tubing from the bulb and join 
the elastic tube. Work the bulb as directed above, 
and observe the character of the flow. 

(5) Join on the coarse capillary and repeat, noting 
the change. 

(6) Replace the coarse capillary with the fine capil- 
lary and repeat. Sum up the results and formulate 
conclusions. 

c. Quantitative tests. 

(7) How much water will be ejected through a fine 
capillary tube in ten seconds in experiment (3) ? 

(8) How much through a fine capillary in the same 
time in experiment (6). 

Note: In performing experiments (V) and (8) great 
care should be used to exert exactly the same force 
upon the bulb. The same capillary should be used in 
the two experiments. 

What is the significance of these two experiments? 

b. The impulse wave. The graphic record. 

/. Appliances. — Support; cork board (about 8 by 10 cm.); 

small glass rod about 20 cm. long; corks; needles; 

kymograph; piece of sheet lead 1 cm. wide and 5 cm. 

long; copper wire No. 16. 

2. Preparation. — Make a tracing lever from the glass 

rod by drawing out one end to a rather fine point 

and drawing the other to about one-half its original 

diameter and bending it to make an angle of 135°. 

Bend up 1.5 cm. of each end of the sheet lead so that it 

will stand at right angles to the middle 2 centimeters; 



100 



LABORATORY GUIDE IN PHYSIOLOGY. 



bore the cork and pass the larger end of the tracing lever 
through it. Fix the cork board to a ring of the support 
with copper wire; fix the sheet lead to one end of upper 
surface of the cork board with copper wire and pass a 
needle through the limbs of the lead bearings and the 
lever-cork in such a way as to bring the lever over the 
middle of the board. The completed apparatus will 
have the relations indicated in the accompanying cut. 
Observations. 
(1) If the finger be held upon this elastic tube while 
the bulb is being rhythmatically squeezed, a series 
of impulses or pulsations will be f<=lt by the finger 




Fig. 16. 



Place one finger upon the elastic tube near the 
bulb, and another three or four feet from the bulb. 
Let the bulb be pumped with sudden, but infre- 
quent contractions. May one note a difference in 
the time of pulsation felt by the two fingers ? If so, 
which is felt first ? Why ? What is the cause of 
the pulsation ? 
(2) To get a tracing of this pulse, pass the rubber 
tube across the cork board under the tracing lever 
[See Fig. 16]; adjust to kymograph and take trac- 
ing. Vary the character of the bulb contractions 



CIRCULATION. 101 

as follows, taking one complete rotation of the 

drum for each variation: 

(a) Slow initial contraction of bulb and slow re- 
laxation 

(<£) Slow initial contraction of bulb and quick re- 
laxation. 

(V) Quick initial contraction of bulb and slow re- 
laxation. 

(a 7 ) Quick initial contraction of bulb and quick 
relaxation. 

(e) Same as d with slow rhythm. 

(/) Same as ^/with rapid rhythm. 
(3) Make a careful study of these tracings and deter- 
mine : 

{a) The characteristic and essential features. 

(£) The accidental and nonessential features. 

(V) The cause of the essential ? 

(d) The cause of the nonessential features? 



XXII. The laws of blood pressure determined from 
an artificial circulatory system. 

/. Appliances.— Two large Y tubes of about 6 mm. lumen ; 
four medium Y tubes, lumen about 4 mm ; eight small 
Y tubes, lumen about 2 mm. ; six thick walled capillary 
tubes, about 3 mm. outside measurement, and lumen not 
to. exceed 1 mm. These capillary tubes should be about 
15 cm. long. Two T-tubes of medium lumen; two 




Fig. 17. 

medium sized glass tubes about lb cm. long. All 
rubber tubing should be thin walled and very elastic, 
and should be in three sizes, corresponding to the glass 
tubes. Two pieces of large size, 75 cm. long, and two 
pieces about half that length ; four pieces of medium 
size, about 40 cm. long ; ten pieces of small size ; bulb; 
heavy linen thread; mercury; large glass receptacle for 
water, two medium sized rubber couplings. 

102 




CIRCULATION. 103 

2. Preparation. — First, make two manometers whose dis- 
tal limb shall be 40 cm. long, and proximal limb 30 cm. 
with a horizontal shoulder 5 cm long. Second, 
draw out the two limbs of the medium Y tube 
until they are about the same in size as the 
small tubing (Fig. 18). Third, construct the 
Fig. 18. artificial circulatory system according to Fig. 17. 
J. Operation. — First, supply the manometers with mercury 
so that there will be 12 to 15 cm. in each limb of the 
arterial manometer, and 5 to 10 cm. in each limb of the 
venous manometer. If the class is not familiar with the 
use and interpretation of the manometer, the demonstra- 
tor should lead them to discover all of its essential 
features. Second, the whole system should be filled 
with water and freed from air before the observations 
begin. Third, care should be taken that no stoppage in 
the system occurs; otherwise the mercury may be 
thrown out of the manometers and lost. 
4 Observations. 

a. The manometer (mercurial). 

(1) Find the actual pressure when the mercury in 
the distal column stands 6 cm. higher than that in 
the proximal column. Derive the following for- 
mula: Actual pressure = 13.6 n r 2 (2 m — ^), when 
r=radius of column of mercury, and m the rise of 
mercury in the distal limb of the manometer. 

(2) Find the pressure per square cm. where the ob- 
servation is the same. Derive the following formula: 
Pressure per unit area = 26.2 m. 

(3) Which of these data (actual pressure or pressure 
per unit area) would be the more valuable to record ? 

(4) After the arterial circulatory system has been 
freed from air and is at rest, do the proximal and 
distal columns of mercury stand at the same level? 



104 LABORATORY GUIDE IN PHYSIOLOGY. 

If not, why? What allowance, if any, should be 
made for this? 

b. Arterial pressure. 

(5) With capillaries 1 to 6 open and tubes 7 and 8 
closed, let one member of the division make strong 
rhythmical contractions of the bulb at the rate of 
about 2 per second. Note effect on manometer. 
Account for all the phenomena. 

c. Venous pressure. 

(6) Note the effect of the contraction upon the venous 
manometer. If there is any change in the manome- 
ter, compare in rhythm and in extent with the 
changes in the arterial manometer. 

d. Relations of arterial to venous pressure. 

(7) Make very slow contractions. Note results. 

(8) Make rapid, strong contractions. Note results. 

(9) Make rapid, weak contractions. Note results. 

(10) Remove the clamps from vessels 7 and 8 (local 
dilatation of arterioles) and repeat experiments 7, 8 
and 9, noting and interpreting results. What effect 
does a dilatation of arterioles have upon venous 
pressure? What effect does it have upon arterial 
pressure? 

e. Pressure formuloz. 
Let: P ^pressure. 

Pa ^arterial pressure. 
Pv =venous pressure. 
H ^strength of contractions. 

Rd = distal resistance beyond point of observation. 
v =velocity at point of observation, 
r =radius of vessel at point of observation. 
How many of the following formulas will your observa- 
tions justify ? 



CIRCULATION. 105 

1. PasoH. 6. PaxHxRd. 

2. PvxH. 7. Paxr 2 . 

3. Pa xRd. 8. PaooHxRdXr 2 . 

4. Pv xRd. 9. Pa xv. 

5. Pa xPv. 10. P xHxRdXr 2 Xv. 

/, Grafic record of pulse tracing from the artificial circula- 
tory system. 

With the recording apparatus used in Chapter XXI or 
with a sphygmograph, or better, with both pieces of 
apparatus, make tracings of the pulsations of the 
arterial tubes "a" and "b." (Fig. 17.) Com- 
pare all tracings carefully and interpret all the 
features of the record, differentiating the essential 
from the nonessential, as before. 



XXIII. The pulse, sphygmographs and sphygmograms. 

i. Appliances. — A sphygmograph; tracing slips; a fish-tail 
gas jet, or kerosene lamp. 

2. Preparation. — Smoke about two dozen tracing slips. 

j. Operation. — That the sphygmograph is so little used by 
the general practitioner may be attributed to the fact 
that hurry of business, or some other cause, has hin- 
dered him from making himself thoroughly conversant 
with the adjustment and use of the instrument, with its 
limitations and with the interpretation of the tracings. 

To adjust the sphygmograph. 

First. Let the observer stand with his right foot on a 
chair. This brings his thigh into a horizontal position. 
Second. Let the subject stand at the right of the ob- 
server, resting the dorsal surface of the left forearm upon 
the observer's knee. 

Third. Let the observer with pencil or pen mark the 
location of the radial artery. 

Fourth. Let the observer wind the clockwork which 
drives the tracing paper; adjust the latter in readiness 
for tracing; rest the instrument upon the subject's arm 
with its foot upon the radial artery and adjust the posi- 
tion, tension and pressure, in such a manner as to obtain 
the maximum amplitude of swing of the tracing needle. 
Take the tracing. Fix. 

^. Observations. 

a. The location, etc., of the radial artery. 

(1) What are the relations of the radial artery at the 
distal end of the radius? 

(2) How may the relations vary? 

106 



CIRCULATION. 107 

(3) Is there any variation, among the members of the 
division, in the location of the radial artery? 

(4) May excessive muscular development affect the 
ease with which the artery may be located and its 
pulsations studied ? 

(5) May excessive deposit of adipose tissue hinder 
the observations of the pulse? 

(6) May faulty position of subject or of his clothing 
affect the pulse ? 

The digital observation of the radial pulse. 

(7) Feel the pulse with the side or back of the finger; 
then with volar surface and tip of each finger of each 
hand and note the finger or fingers with which the 
feeling is most acute. It will be wise to always use 
these fingers in all tactile examinations. Their 
acuteness of feeling will increase with practice. 
One may thus acquire the educated touch — tactus 

ERUDITUS. 

(8) How much may be learned of the pulse by means 
of the touch alone ? Observe and note (#) fre- 
quency; (b~) rhythm; (r) volume; (d) strength; (e) 
compressibility. (/) May anything else be deter- 
mined by this method ? 

The Sphygmogram. 

(9) Take at least three pulse tracings of each indi- 
vidual in the division, {a) Compare the tracings 
taken from one individual; if they differ, determine 
the cause of the difference. (<£) Compare tracings 
of different members of the division. Determine, if 
possible, the causes of the differences. 

(10) Do variations of the relations of the artery affect 
the sphygmogram? Does the adjustment of the 
instrument affect the sphygmogram ? Does the 



108 LAB OR A TOR V G U1DE IN PHYSIOLOG Y. 

elasticity of the artery affect the tracing ? How 

does strength or rate of heart-beat affect it? 

Make a list of the facts regarding the condition of the 

circulatory system which maybe determined with the help 

of the sphygmograph. Make a list of the precautions 

necessary to observe in the use of the sphygmograph. 



XXIV. To determine the general influence of the vagus 
nerve upon the circulation.* 

i. Appliances. — Operating case, (Appendix, A-3); a pair 
of curved, blunt-pointed shears, or better, a pair of 
barber's clippers; a rabbit board; large sheet of heavy 
paper; sealing wax; cotton; ether; thread; 1 Daniell 
cell; inductorium; vagus electrodes; 2 Du Bois keys; 7 
wires; stethoscope; a strong, adult rabbit. 
2. Preparations. — Let the six students be subdivided into 
three groups of two students each. 

Let group "a" be responsible for the anaesthesia. 
Use the sheet of heavy paper to make a conical hood, 
whose spiral turns may be held in place with sealing 
wax. Place a wad of cotton loosely in the mouth of 
the cone. 

Let group "&" perform the operation. Fix the rab- 
bit, back downward, upon the holder; fix the nose in 
special holder (see Fig. 19); with the barber's clippers 
remove the hair from ventral side of thorax and neck ; 
make hands and instruments clean, place instruments 
in a shallow basin of warm, 1 per cent carbolic acid 
solution; cut two or three ligatures of thread and 
place them in the instrument basin. 

Let group li c " arrange the electrical apparatus for 
stimulation of the nerves. Fill the cell; join up with 
contact-key in the primary circuit, and a short-circuit- 
ing key in the secondary circuit. Test the apparatus to 
see if everything is in order. 
J. Operation. 

Group "a." (1) Pour 2 cc. or 3 cc. of sulphuric 

*Let six students work together. 

109 



110 LABORATORY GUIDE IN PHYSIOLOGY. 

ether upon the cotton in the cone; place the cone over 
the rabbit's nose; observe, and note carefully every step 
in the anaesthesia. 

(2) Carefully note the rate of the heart before begin- 
ning anaesthesia. 

(3) Keep the cotton moist with ether; watch the 
respiration and pulse, and be careful not to give the 
animal too much and interrupt the experiment. 

Group " b." Wash the clipped surface of the throat. 

After the rabbit is completely anaesthetized, make 
with scissors a median incision through the skin, be- 
ginning at the apex of the sternum and cutting anteriorly 




Fig. 19. 

for about 5 or 6 cm., divide the subcutaneous connec 
tive tissue over the middle of the trachea. Carefully 
separate from the median line on either side laterally 
the subcutaneous connective tissue with the associated 
adipose tissue. 

How many pairs of muscles come into view ? What 
two muscles approach the median line to form the apex 
of a triangle at the anterior end of the sternum ? Ob- 
serve a pair of thin muscles lying dorsal to the muscles 
just mentioned and joining in the median line to form a 
thin muscle sheet covering the trachea on its ventral 
side ? What muscles are these ? 

Carefully lift up the median edge of the sterno mas- 
toid muscle and separate with the handle of a scalpel 



CIRCULATION. Ill 

or a seeker the delicate intermuscular connective tissue. 
A blood vessel and several nerves come into view. 

Is the blood vessel an artery or a vein ? How many 
large nerves accompany the blood vessel ? 

Take hold of the sheath of the vessel, lift it up and 
note in the connective tissue accompanying the blood 
vessels two nerves, one large and one small. When the 
artery is in its normal position, what relation do these 
two nerves sustain to it? Which of the two nerves is 
external and which is dorsal to the bloodvessel? Which 
is in close relation to the artery? What is the name of 
each of the nerves? 

In preparing the nerve for stimulation one should 
neither grasp it with the forceps nor with the fingers. 
It may be separated from the delicate connective tissue 
in which it lies by use of a blunt seeker. Far better 
than any metallic instrument is a small glass rod drawn 
to a point, curved and rounded in the Bunsen lamp 
(see Fig. 11-A). Prevent the tissues drying up by 
occasionally pressing them lightly with pledgets of 
cotton moistened with normal salt solution. 

Adjust the electrode carefully upon the vagus and see 
that no unnecessary tension is allowed to be exerted 
upon the nerve. It is usually necessary to hold the 
electrode in place during the observations. 

Observations, 
a. Ancesthesia. (Observations by Group "#.") 

(1) Are you able to make out different stages in anaes- 
thesia? 

(2) How many stages did your animal manifest? 

(3) Give the characteristics of each stage. 

(4) What effect did the ether have upon the rate of 
heart beat? 

(5) What effect did the ether have upon the respira- 
tion? 



112 LABORATORY GUIDE IN PHYSIOLOGY. 

b. The stimulation of the vagus. (Observations by 
Group " <:.") 

(6) Stimulate moderately one vagus. Note with a 
stethoscope whether the rate of the heart is in- 
creased. 

(7) Cut both vagi high up in the neck. Note the 
rate of heart beat at intervals of five minutes for 
twenty minutes, allowing the rabbit to partially 
recover from the anaesthesia. 

(8) Stimulate one vagus. Compare the result with 
that obtained under experiment (6). 

(9) Will very strong stimulation bring the heart to a 
standstill ? 

(10) If the heart was brought to a complete stand- 
still by the stimulation, will it start up again spon- 
taneously when the stimulus is removed? Will the 
rate reach the degree of acceleration observed in 
experiment (7)? 

(11) Sum up the observations into a concise state- 
ment as to the influence of the vagus upon the 
heart. 

Note: Dispatch the rabbit with chloroform. 



D. RESPIRATION. 



IX. a. External respiratory movements, b. Intra=thor= 
acic pressure, c. Intra=abdominal pressure. 

i. Appliances. — Operating case; clippers; rabbit board; 
rabbit; cone for anaesthesia; ether; kymograph; cardio- 
graph, which may, in this case, be called a rabbit stetho- 
graph; three recording tambours; 10 cm. of glass tubing, 
3 mm. lumen; rubber tubing to match; chronograph. 

2. Preparation. 

(i) Fix and anaesthetize rabbit. 

(2) Clip ventral aspect of rabbit's thorax and abdomen. 

(3) Prepare thoracic and abdominal cannulas by drawing 
the glass tube slightly in the center, cutting diagonally 
at the middle, smoothing diagonally on an emery stone. 

(4) Join a 30 cm. piece of rubber tubing to each cannula 
at the larger end, and clamp it near the cannula. 

J. Operation. 

a. External respiratory movements. 

Place the button of the rabbit stethograph upon the 
ventral surface of the rabbit as near as possible over the 
junction of the diaphragm with the body wall, and a lit- 
tle to the right or left of the median line. So adjust the 
stethograph as to obtain the maximum excursion of the 
recording lever. The stethograph may be held in posi- 

1X3 



114 LABORATORY GUIDE IN PHYSIOLOGY. 

tion through the agency of a clamp and support; some- 
times, however, better results may be secured by holding 
the stethograph in the hands, supporting the wrists on 
the edge of the rabbit board. 

b. Intrathoracic pressure. 

Locate an intercostal space to the right of the ster- 
num and opposite its middle point. Make an incision 
0. 5 cm. long, parallel with the intercostal space and 1 cm. 
from the sternum. Dissect through the intercostal mus- 
cles, taking care not to cut the pleura. Insert the point 
of the glass cannula into the wound, press it carefully 
through the pleura into the right pleural cavity. 

Join the rubber tube to a recording tambour and un- 
clamp. Slowly and gently manipulate the cannula until 
there is evident communication through the lumen of the 
cannula and tube from the pleural cavity to the tambour. 

So adjust the cannula that the recording lever makes 
the maximum excursion. Bring the levers into such a 
relation to the kymograph that the tracing point of the 
stethograph lever shall be vertically over that of the 
lever which is to record intra-thoracic pressure, and about 
two centimeters from it. 

c. Intra=abdominaI pressure. 

Make, in the median line of the abdomen, a one-cen- 
timenter incision, limited anteriorly by the xiphoid ap- 
pendix. After partially dissecting through the abdom- 
inal wall insert the cannula into the incision and care- 
fully press it through the peritoneum. If one push 
the cannula between the diaphragm and liver he will 
usually be successful in getting the free end of the can- 
nula into an open space. Care should be taken not to 
wound the liver. Take tracing as in b. 
<f.. Observations. 

a. External respiratory movements. 



RESPIRATION. 115 

(1) During one revolution of the drum — 5 minutes — 
note the rate and rhythm of the respiratory move- 
ments as recorded by the stethograph, and chrono- 
graph. 

(2) Does the stethogram show anything more than 
rate and rhythm ? 

(3) What phase of a respiratory cycle does a rise of 
the lever indicate ? 

(4) What is the relative duration of inspiration and 
expiration as indicated by the stethogram? 

(5) Does the stethogram indicate any variation indif- 
ferent parts of the inspiratory act ? Of the expira- 
tory act ? 

(6) Differentiate the essential from the nonessential 
in the stethogram and determine as far as may be, 
the cause of each. 

Intra-thoracic pressure. 

Trace upon the drum a stethogram and chronogram 
as well as an intra-thoracic pressure record, taking 
care that the tracing points of the recording tam- 
bours are in a vertical line. 

(7) Does the rhythm of varying pressure correspond 
to the rhythm of the respiratory movements? 

(8) If so, does that necessarily establish between them 
the relation of cause and effect? 

(9) What change of pressure is indicated by the rise 
of the pressure lever? 

(10) What movement of the pressure lever corre- 
sponds to a rise of the stethograph lever? 

(11) What is the condition of intra-thoracic pressure 
during inspiration ? During expiration ? 

(12) Stop the entrance of air into the respiratory pas- 
sages by closing the rabbit's nostrils. What effect 
does this have upon the respiratory movements? 



1 16 LAB OR A TOR Y G UIDE IN PHYSIOL OGY. 

(13) Is the intra-thoracic pressure affected by the ex- 
periment ? If so, explain the effect. 

(14) If two phenomena correspond perfectly in their 
cycles, and if a variation of one is always accom- 
panied by a variation in the other, can there be any 
reasonable doubt that they sustain to each other the 
relation of cause and effect ? 

(15) Is one of the phenomena in question the cause 
of the other? If so, state which is the cause and 
establish your position. 

To measure intra thoracic pressure. 

(16) Clamp the rubber tube of the pressure appa- 
ratus. Replace the recording tambour with a water 
manometer. Unclamp. 

Is the pressure during inspiration positive or negative, 

and how much ? 
(1*7) Is the pressure during expiration positive or 

negative, and how much? 

(18) If the whole apparatus were filled with water 
instead of air and water, would it make any essen- 
tial difference in the result ? What effect do the 
variations of the intra- thoracic pressure have upon 
the circulation ? Upon the respiration ? 

c. Intra-abdominal pressure. 

Trace upon the drum a stethogram and chronogram as 
well as a record of the intra abdominal pressure. 

(19) Does the rhythm of varying intra abdominal 
pressure correspond with the rhythm of the respira- 
tory movements ? 

(20) With what phases, respectively, of the respira- 
tion do rise and fall of the intra-abdominal pressure 
correspond ? 

('21) What influence upon the circulation would rise 
of the intra-abdominal pressure exert? 



RESPIRATION. 117 

(22) Make a quadruple tracing: stethogram, chrono 
gram, intra-thoracic pressure and intra-abdominal 
pressure. 

(23) Sum up the work of the day in a series of con 
elusions. 

(24) Dispatch the rabbit with chloroform, noting the 
respiratory changes induced by the lethal dose of 
chloroform gas. 



XXVI. Respiratory movements in man. a. The stetho=» 

graph, b. The thoracometer. c. The belt= 

spirograph, d. The stethogoniometer. 

/. Instruments. — Besides a kymograph and a chronograph, 
the following: 
Stethograph. — An instrument for recording graphically 

the movements of the chest-walls [Gould]. 
Thoracometer. — An instrument for measuring (and 
recording) the movements of the chest- walls [Gould]. 
Belt-spirograph. — An appliance for recording respira- 
tory changes in thoracic or abdominal girth. 
Stethogoniometer. — An instrument for measuring the 
curvature of the chest [Gould]. 
2. Appliances needed in the adjustment and use of these 
instruments.- — Heavy base support; three large clamp 
holders; iron rod, 8 or 10 mm. in diameter and 50 cm. 
long; two wooden or iron rods, 1 cm. in diameter and 
40 c. m.long; a receiving tambour ; a recording tambour, 
with support; two medium clamp holders; two uni- 
versal clamp holders; simple myograph; 1^ meter 
fine fish cord; two pulleys, 
j. Preparation. — F 'or construction of apparatus see Appen- 
dix A, 10-13. 

Adjustment of the apparatus. 
a. The Stethograph. 

Clamp the center of the iron rod to the heavy base 
support. Clamp the wooden rods to the iron 
rods so that they will extend out to one side of the 
iron rod in a horizontal plane. Figure 20 shows the 
stethograph ready for use. 

118 



RESPIRATION. 



119 



Let a member of the division remove all clothing 
above the waist and be the subject of observation for 
the other members. In making observations with the 
stethograph the subject should sit with his back or 
side to the table. The observer may readily adjust 
the stethograph to record the changes of any lateral 
or dorso-ventral diameter of the thorax. For all 
observations upon the respiratory changes in the 
thorax, the subject should keep the parts of the body 
symmetrically disposed. 




Fig. 20. 

Observations. 
<T) How much may be learned of man's respiratory 
movements by simple inspection? Make a careful 
enumeration and record. 

(2) Adjust the stethograph and make a record — a 
stethogram — of the changes of the lateral diameter 
of the thorax at the ninth rib. 

Does the stethograph show more than could be 
learned from inspection? If so, what? 

(3) Take a stethogram of the lateral diameter at the 
sixth rib. How does it differ from the ninth rib 
stethogram ? Account for the difference. 



1 20 LAB OR A TORY G UIDE IN PH YSIOL OGY. 

(4) Take a stethogram of the dorso ventral diameter 
of the thorax over the lower end of the gladiolus. 
Compare. 

(5) Take a lateral ninth rib stethogram while the 
subject reads a paragraph; sighs; coughs; and 
laughs. Account for the peculiarities. 

(6) Take a lateral ninth rib stethogram after the sub- 
ject has taken vigorous exercise. What changes 
are to be noted ? 

(*7) After a similar series of stethograms have been 
taken for others, compare; determine the essential 
features; give causes of these. 
(8) Seek the causes of the difference which exist be- 
tween stethograms of different individuals. May 
they be accounted for by stature, condition, occupa- 
tion or habit ? 
b. The thoracometer. — Remove from the stethograph 
the wooden rod which bears the receiving tambour, 
and slip the iron rod of the apparatus described in 
Appendix All into the same place with the button 
inward. The accuracy of the apparatus is increased 
if the heavy support which bears the spiral spring, 
just fixed in position, bear also the recording lever. 
Use a simple myograph lever which may be clamped 
to the support. The cord which runs over the pulley 
beneath the spring must change direction at least 
twice after leaving the first pulley. One will need 
two more pulleys such as the one described in the ap- 
pendix. They may be held in position by clamp 
holders. If one use a horizontal drum, however, the 
cord may pass from the first pulley direct to the lever. 
In either case one would need to pass an elastic band 
around the short arm of the myograph lever in such a 
way as to draw the lever in a direction opposite to that 



RESPIRA Tl ON. 121 

given it by the spiral spring. In every case the elas- 
ticity of the elastic band must be less than that of the 
spiral spring, otherwise the rubber button would not 
follow the movements of the thoracic wall. So adjust 
the apparatus that every movement, however slight, 
of the button will be instantly responded to by the 
lever. 
^4') Observations. 

(9) Carefully measure the arms of the lever to deter- 
mine how much the tracing point of the lever will 
move for every millimeter that the button moves. 

(10) When the button is pressed outward in inspira- 
tion what direction does the lever move? 

(11) Take tracings of the changes in the dorso ven- 
tral diameter at the level of the nipples. Deter- 
mine by measuring the tracing how much the 
dorso ventral expansion is. What is the average 
expansion during normal, quiet breathing ? What 
is the expansion during forced respiration ? 

(12) Make a similar series of observations on the 
lateral diameter in the plane of the nipples. 

(13) Repeat observations on the lateral ninth rib 
diameter. 

c. The belt=spirograph. — Substitute for the rod of the 
thoracometer which bears the button and spring, a 
plain wooden or iron rod. Place the belt-spirograph 
around the subject at any level of the body, whose 
varying girth is to be observed. The fish cord used 
in the previous experiment may be transferred to this 
instrument. Tie one end into the eye in pulley No. 1, 
pass it over the other pulleys and to the lever; the 
horizontal bars may be raised to the axillae and will 
serve to steady the subject. The expansion in girth of 
thorax is so great that it may be found necessary to 



122 LABORATORY GUJDE IN PHYSIOLOGY. 

change the relative lengths of the lever-arms to avoid 
too great an excursion of the writing point of the 
lever. 
(-£") Observations. 

(14) How many millimeters will the point of the 
lever rise or fall for every centimeter that the girth 
increases? 

(15) What is the average expansion of the thorax 
during normal quiet breathing? 

(16) During five minutes — 75 or 80 respirations — are 
all of the respirations practically the same or are 
there occasionally deeper breaths? If the latter is 
observed is there any regularity in the occurrence 
of deeper respirations ? How may occasional deep 
respirations be accounted for? 

(17) Let the subject make a series of forced respira- 
tions. What is the maximum expansion? What is 
the average expansion of the series? 

d. The stethogoniometer. 

This instrument is described in Appendix A 13. Its 
purpose is to record the outline of any horizontal 
section of the thorax, though it could be used as well for 
tracing the periphera of the abdomen, of the head, or of a 
limb. To use the stethogoniometer for the purpose here 
intended let the subject sit beside a table upon a 
stool adjustable for height. So adjust the stool as to 
bring the circumference of the thorax to be observed 
even with the upper surface of the table. Fix the 
point c, of the instrument, to the table. Let the ob- 
server locate, with pen or pencil, upon the side of the 
subject distal from the table, a point which shall serve 
as a starting point. 

When the point b, of the instrument, rests upon 
this point of the subject's thorax the instrument 



RESPIRATION, 123 

should be well extended, somewhat more than repre- 
sented in the figure. Fix a sheet of paper to the table 
under the recording pencil at a. To take a graphic 
record of the contour of the thorax, proceed as follows: 

(18) (a) Let the observer place the tracing point b 
upon the "starting point" in the distal side of 
the thoracic perimeter. 

(£) Sweep the tracing point quickly around one- 
half the perimeter to a point approximately oppo- 
site to the starting point. 

(7) Rotate the curved arm of the instrument upon 
its axis bx, through 180°. 

(d) Sweep the tracing point around the other one- 
half of the perimeter to the starting point. 

(<?) The movements of the tracing point, b, in the 
horizontal plane have been faithfully recorded 
upon the sheet of paper by the recording pencil 
at a. It is hardly necessary to remind the student 
that the subject must remain motionless during 
the observation. 

(19) Take a thoracic perimeter with the chest in re- 
pose. Measure different diameters of the tracing 
and multiply by five to reduce to actual measure- 
ments. 

(20) Take a tracing at end of forced expiration; at 
end of forced inspiration. Compare diameters. 

(21) Make a series of these tracings for different in- 
dividuals. Compare. 

(22) Formulate conclusions. 



XXVII. Respiration in man; lung capacity and strength 

of inspiration and expiration; chest measure* 3 

ments; the preservation of the data. 

/. Instruments. — Spirometer; pneo-manometer; meter tape; 
steel calipers; standard, with horizontal arm for meas- 
uring height; scales for taking weight. 

2. Observations. 

(1) Test with the spirometer the lung capacity of each 
member of the division. May differences in lung ca- 
pacity be accounted for by difference in stature, condi- 
tion, occupation or habit? 

(2) Take with the tape the girth of chest over the nipples 
in a plane at right angles with the axis of the thorax. 
(a) With chest in normal repose. 

(£) At the end of forced expiration. 
(V) At the end of forced inspiration. 

(3) Take the girth of chest over the juncture of the 
ninth rib with its cartilage, holding the tape in a plane 
at right angles with the axis of the thorax. 

(a) With the chest in repose. 

(<£) At the end of forced expiration. 

(V) At the end of forced inspiration. 

(4) With the calipers measure the dorso-ventral diameter 
at the level of the nipple, holding the calipers in a 
plane perpendicular to the axis of the thorax. 

{a) Normal, (£) after expiration, (7) after inspiration. 

(5) Take the lateral diameter in the nipple-plane. 

{a) Normal, (£) after expiration, (V) after inspiration. 

(6) Take the lateral diameter at the ninth rib. 

(a) Normal, (£) after expiration, (V) after inspiration. 

124 



RESPIRA TION. 125 

(7) Test with the pneo manometer the force of inspira- 
tion and expiration. (Appendix, A 14). Let each 
member of the division test with the pneo-manometer 
the maximum positive pressure which he is able to 
produce in the respiratory passages during expiration. 

(8) Test with the same instrument the maximum nega- 
tive pressure which each individual can produce 
during inspiration. 

(9) Does the face become red in either of these tests? 
If such is uniformly observed, account for it. 

(10) The preservation of data. Experience has shown 
that when data are to be preserved for subsequent use 
in the comparison of one class of individuals or cases 
with another, it is very much more economical in time 
to record the data upon cards. 

For the above data one may use such a card as is 
appended to this chapter. 

In addition to the measurements above given record 
upon the cards the weight, the height, the bodily condi- 
tion of the individual, and especially whether the indi- 
vidual has lived in a hilly or in a flat country, and 
whether he has been active or inactive. 

Name 

Age Weight 

Condition: Fat, medium or lean. 

Muscular development 

Previous occupation . . 

Home Flat or hilly region. 

Habit: Inactive, active, (tennis, bicycle ) 

Lung capacity Height 

Girth of chest in repose 

Girth of chest at end of forced inspiration . . . , . 

Girth of chest at end of forced expiration 

Girth of chest at ninth rib, repose 



126 LABORATORY GUIDE IN PHYSIOLOGY. 



Girth of chest after forced inspiration 

Girth of chest after forced expiration 

Diameter of chest dorso-ventral, in repose 

full empty 

Diameter of chest, lateral, in repose . . full 

empty 

Observer 

Date 



XXVIII. The evaluation of anthropometric data. 

A large proportion of the problems that the medical 
man has to solve involves the finding of averages of a 
large number of observations. This is sure to be true of 
all anthropometric problems. In the course of the pre- 
ceding lesson valuable anthropometric data were collected 
and recorded upon cards. The value of this material is 
purely potential. Before the data will furnish a basis for 
drawing conclusions it is necessary to subject it to a pro- 
cess of evaluation. This process consists, first, in group- 
ing; second, in getting the average or the median value 
for each measurement; and, third, in graphically repre- 
senting the averages. In the previous lesson the observer 
noted upon each card whether the subject had lived in a 
hilly or in a flat country; further, whether he had led a 
physically active or inactive life. This gives one an op- 
portunity for four groups when the cards from the whole 
class are collected. 

Group I. Active men from a hilly country. 
" II. " " " flat 

" III. Inactive " " hilly " 

" IV. " " " flat " 

Until recently it has been customary to simply write 
the data for any group in columns and " strike an average" 
of each column. If there are only 10 to 20 or 30 individ- 
uals in each group this method does not entail the unnec- 
essary expenditure of much energy, but it is not reliable; 
for one " giant " or "dwarf " in any group would vitiate 

127 



128 



LABORATORY GUIDE IN PHYSIOLOGY. 



the whole result. If there aie 100 or 1000 individ 
uals in a group, then the use of the old method of finding 
the arithmetrical average is exceedingly wasteful of both 
time and energy. It must be added, however, that when 
the number of observations is large the chances are that 
there will be as many dwarfs as giants, thus making the 
average approximate closely the median value. It is the 
latter that we are seeking, viz.: the mediate value; this 
may be defined as that value which is so located in 
the whole series of observations, in a single measurement 
of any group, that there are as many below it as above it, 
i. e., that trie numbers of values which it exceeds is equal 
to the number of values which exceed it. 

Let us take a concrete case. In a group of 316 seven- 
teen-year-old boys certain physical measurements were 
recorded upon individual cards. Let us take for an ex- 
ample the ginh of head recorded in centimeters and tenths. 
Instead of writing in a column the 316 head- girths, each 
expressed in three figures, adding and averaging, let us 
adopt the new method first suggested by the Belgian as- 
tronomer and ' anthropologist, Quitelet, and later elabo- 
rated by Gaiton, the London anthropologist.* Arrange 
the cards in piles, placing in one pile all of the cards 
having girth of head 51-f- centimeters, in another pile all 
having 52 — j— centimeters, and so on. In the case in ques- 
tion it was found that the 316 cards were quickly distrib- 
uted, falling into the following groups: 



GIRTH OF HEAD. 



NO. OF OBSERVATIONS 

(No. of Cards.) 



51+52+ 



1 



53+ 
17 



54+ 
41 



55+ 



70 



6+57+ 



74 



60 



58+ 



29 



59+60+ 
10 



* For a more extended explanation and development of this method 
than given in this chapter see also " Changes in the Proportions of the 
Human Body" — Hall. Journal of the Anthi opological Institute of Great 
Britain and Ireland. London, August, 1895. 



RESPIRA TION. 1.29 

The problem is to find the value of the median measure- 
ment or the median value. There are 158 values below 
the median and as many above. 

First. To locate the median observation : This is equiv- 
alent to saying — find in the lower series of numbers 
(1-7 -17, etc.) the 158th observation from either end. It 
must be located in the pile of cards which numbers 74. 
This group may be called the median group. But where in 
this group is the median observation located? In order to 
determine this, add the groups at the left of the median 
group, these may be called the minus groups, the values 
which they represent being less than that of the median 
group. l + 7-|-l74-41 + 70 = 136. To this sum one must 
add 22 observations from the median group to make 158. 
The median observation is then located in the median 
group, 22 points from the left. 

Second. To evaluate the median observation we must 
take it for granted that the 74 observations of the median 
group are evenly distributed over the distance between 56 
cm. and 57 cm. That being the case the median value 
would be 56ff cm. 

Let us put a general proposition in the form of an al- 
gebraic formula. 

Let M = the number of observations in the median 
group. 

Let n = the total number of observations. 

2p = the sum of the plus groups. 

2m = the sum of the minus groups. 

a = the minimum value of the median group. 

d = the arithmetric difference in the minimum values 
of the groups. 

p. = the median value to be determined. 

d(-|~2m) d(^--Sp) 

Then y. ,= a -\ = or p. = a + d = 1 



130 LAB OR A TOR Y G UIDE IN PH YSIOL O G Y. 

Apply this formula to the case taken for example : 

1(-^-- 136) 
fi = 56 H -fa = 56.3. 

or 

1 (^L _ 106 ) 

fi — 57 ^ '-— 57 — 0.703 = 56.3. 

After one has found the median value for each 
measurement in each group, these may be tabulated and 
the values compared. When the table of median values 
is large it is almost necessary to carry the work of reduc- 
tion a step farther and represent these values graphically 
in a chart. Another opportunity will be used for giving 
the methods used in the graphic representation of statis- 
tical tables. 

The table which results from the data collected in 
connection with the previous lesson is not so large but that 
the observer can practically comprehend the whole at a 
glance. 

Our grouping enables us to answer the following ques- 
tions : 

First. Has general physical activity any essential in- 
fluence in the development of the respiratory organs and 
function ? 

Second. Is the climbing of hills during early life a 
factor in the development of the respiratory organs and 
function ? 

If both of these questions may be answered affirma- 
tively then one would expect to find that the median values 
of group I, (active individuals from a hilly country) uni- 
formly exceed the values of group II; and that those of 
group III uniformly exceed those of group IV, but that 
the median values of group II may or may not exceed 
those of group III. 

The following conclusions are quoted from a student's 
note book : 



RESPIRA T10N. 131 

(1) ''Every measurement of the 'median ' active man 
is greater than the corresponding measurement of the 
1 median ' inactive man." 

(2) "Every measurement of the median active man 
from a hilly country is greater than the corresponding 
measurement of the median active man from a flat coun- 
try." 

(3) "But the active flat country men exceed in their 
median measurements the inactive hill country men, 
therefore, physical activity is a stronger factor in the devel 
opment of respiratory organs than is the topography of 
the habitat." 



XXIX. The action of the diaphragm. 

/. Appliances. — Operating case; clippers ; rabbit board, or 
dog board ; rabbit or dog ; ether ; ether cone ; absorbent 
cotton; kymograph ; chronograph ; recording tambour; 
beaker with warm water; medicine dropper or bulb. (If 
a dog be used, the medicine dropper will not be large 
enough, its place may be taken by a soft spherical rub- 
ber bulb about 2 cm. in diameter.) Inductorium, 1 cell, 
2 keys, vagus electrode, 5 common wires and 2 fine 
wires. Sometimes the bulbs mentioned above, and usu- 
ually used for this purpose, are not satisfactory. Very 
good results may be gotten by using a piece of glass rod, 
which has been rounded at one end and sharpened at 
the other, as a lever. (Fig. 21.) The rounded end is 
passed through the abdominal wall and rests against the 
diaphragm, (aT). The point is inserted into the cork 
button of a tambour. Any contraction of the dia- 
phragm presses the round end down, the body wall 
serves as a fulcrum (/), the point is pressed up and the 
lever of the recording tambour rises. 

2. Preparation. — Fix the animal to the board; anaesthetize; 
clip anterior median, region of abdomen. Put the bulb 
into the warm water, join the glass tube of the bulb to the 
recording tambour through a rubber tube. This appa- 
ratus thus joined may be called a phrenograph and its 
record a phrenogram. 

Set up electrical apparatus with short-circuiting key 
in secondary coil. 

j. Operation. — From the posterior extremity of the 
xyphoid appendix make a median incision through the 

132 



RESPIRATION. 133 

abdominal walls. If the lever be used the incision 
should be just large enough to admit the lever, and 
should be located in the angle between the xyphoid and 
the costal cartilages on the right side. 

Clamp with the serre-fines any small vessels which may 
be oozing. After having clamped the rubber tube, which 
connects the bulb to the tambour, carefully insert the 
warm, wet bulb between the diaphragm and the liver. 
The liver will usually afford sufficient resistance to cause 
alternate compression and relaxation of the bulb and a 
consequent rise and fall of the recording lever; if such 
be not the case, the liver may be held in place by two 




Fig. 21. 

Fig. 21. Glass lever for transmitting movements of the diaphragm (I) 

to the receiving tambour. The abdominal wall forms the 

fulcrum (/") of the lever. 

fingers inserted through the incision. In the meantime 
let another member of the division dissect out the left 
phrenic nerve. Fig. 22 shows the relation of the phrenic 
at the base of the neck, in the rabbit. 
4. Observations. 

a. Tactile observation of the diaphragm. 

(1) In what condition is the diaphragm during inspi- 
ration ? Expiration ? 



134 



LABORATORY GUIDE IN PHYSIOLOGY. 



(2) In what position is the diaphragm during these 
two phases of respiration ? 

(3) What parts of the diaphragm make the greatest 
change of position during inspiration ? 

(4) What causes the diaphragm to arch anteriorly 
during normal expiration? Are the conditions 
changed during the present observations? 




fflnlfas, 
'fShchialPlex. 



Fig. 22. 



(5) Are the diaphragmatic movements synchronous 
with the costal movements? 

The normal phreno gram. 

(6) Take a phrenogram. What may be learned 
from it? 

(7) Without varying the adjustment of the phreno- 
graph bulb, take a tracing while repeatedly inter- 



RESP1RA TION. 135 

rupting the respiration by holding the nostrils 
What does the phrenogram show? What is the 
interpretation? 

What effect upon intra thoracic pressure would 
the holding of the nostrils have? 
The phrenic nerve and its junction. 

(8) Describe minutely the relations of the nervus 
phrenicus in the neck. 

(9) Cut the nerve while tracing a phrenogram from 
the left side of the diaphragm. Note the result. 

(10) Take a phrenogram from the right side of the 
diaphragm. Does it differ essentially from the 
normal? 

(11) While taking a left phrenogram stimulate the 
distal end of the left phrenic nerve. Interpret the 
result. 

(12) While taking a right phrenogram stimulate the 
distal end of the left phrenic nerve. Interpret the 
result. 

(13) Dissect out and cut the right phrenic nerve. 
Does the diaphragm cease to move? If it moves, is 
its movement active or passive? Account for the 
phenomena. 

Kill the animal with chloroform. 



XXX. Respiratory pressure. 

i. Appliances. — Operating case; clippers; rabbit board; 
ether; ether cone; absorbent cotton; rabbit stethograph; 
kymograph; a small mercury manometer, to the prox- 
imal limb of which is* attached a thick walled rubber 
tube, a piece of glass tubing for a mouthpiece; a screw 
clamp; chronograph; two recording tambours; rabbit. 

2. Preparation. — Fix and anaesthetize the rabbit, and clip 
the ventral surface of the neck. Join up the manometer 
as shown in Fig. 23. 

j. Operation. — Make a longitudinal incision over the 
trachea. Carefully pass a strong linen ligature under 
the trachea. Make a median ventral slit in the trachea 
anterior to the ligature. Pass through the slit the limb 
of the Y-tube marked 1. (Fig. 23.) Ligate. 

4. Observations. 

a. Respiratory pressure. The pneumatogram. 

(1) After the ligature is tied how does the rabbit 
breathe? Are the thoracic and abdominal move- 
ments of respiration accompanied by other respira- 
tory movements? 

(2) With tube n (Fig. 23) open is there any variation 
of the mercury during respiration? 

(3) With a screw clamp slowly close tube n. As 
the resistance to the flow of air increases what 
change is noted in the manometer? 

(4) Quickly clamp tube n at end of expiration and 
carefully note the manometer reading. Is it posi- 
tive or negative? 

136 



RE6PIRA TION. 



137 



(5) Clamp tube n at the end of inspiration. Is the 
pressure positive or negative? 

(6) You have been determining certain facts regard- 
ing respiratory pressure. Are the causes of the 
changes of respiratory pressure the same as the 
causes of the changes of intra-thoracic pressure ? 

(7) In what way does respiratory pressure differ from 
intrathoracic pressure? 

(8) Disjoin the manometer and join its tube to a re- 
cording tambour and trace a pneumatogram, with 
stethogram and chronogram. 

(9) Compare the pneumstogram with the tracing of 
intra-thoracic pressure. Account for all differences. 



i Cenfimete 
j Scale 



Fig. 23. 

(o) Stimulation of the pulmonary vagus. 

(10) Count the pulse. Adjust the stethograph, re- 
place the manometer, and during the tracing of a 
stethogram place the mouth over the glass mouth- 
piece; quickly blow into the tube (n) until the 
manometer indicates two centimeters of intra 
pulmonary pressure; clamp, count the pulse. After 
a few seconds release the clamp and let the rabbit 
breathe normally for a few minutes. 

Repeat the experiment. Vary by producing in turn 
3 cm., then 4 cm. and finally 6 cm. of intra-pul- 
monary pressure, Fix the stethogram and com- 
pare. 



138 L AB OR A TOR V G VIDE IN PHYSIOLOGY. 

(11) Compare your results with those obtained from 
other rabbits. What are the essential features of 
the modified stethogram ? Formulate conclusions. 

(12) What effect has a sudden increase of intra- 
pulmonary pressure upon the rate of the heart's 
action. 

(13) What nerve is distributed to both lungs and 
heart? Admitting that it is possible for the ob- 
served effects to be produced through the agency 
of the nerves just named, state how this action may 
be accomplished. 

(14) Could the effects be produced in any other way 
than in that which you have given ? 

(15) Is the demonstration unassailable; if not, what 
experiments would lead to results conclusive for or 
against the theory? 

(16) Is the minimum intra-pulmonary pressure, 
which typically modified the stethogram, greater or 
less than the respiratory pressure of forced ex- 
piration ? 

(17) What effect upon intra- thoracic pressure would 
the induction of high intra-pulmonary pressure 
have? 

(18) What effect upon blood flow would high intra- 
pulmonary pressure accompanied by repeated acts 
of forced expiration have? What incident effect 
upon the rate of heart beat? 

(19) Dispatch the rabbit with chloroform after first 
arranging the apparatus for a pneumatogram. 
While holding the mouthpiece over or in a chloro- 
form bottle or sponge, take a characteristic pneu- 
matogram of chloroform poisoning. 

c. The elasticity of the rabbit'' 's lungs. 

(20) After the death of the rabbit open the thorax 



R ESP IRA TION. 1 39 

freely, taking care not to wound the visceral pleura. 
The lungs will collapse. Why? 

(21) Replace the manometer, gently blow into the 
mouthpiece until the lungs have been inflated 
to their normal size. Measure carefully the rise of 
mercury in the distal column. 

What degree of positive respiratory pressure will 
the elasticity of the lungs alone cause. 

(22) What is the significance of the elasticity of the 
lungs in respiration ? 

d. The cardio-pneumatogram. — Remove the tube n from 
the Y-tube, join it to a recording tambour. 

(23) Let a member of the division sit in perfect 
repose, and while the drum of the kymograph 
rotates very slowly, hold the mouthpiece between 
the lips. Hold the nose and suspend all respiratory 
movements for a period. Let some member of the 
division count the pulse of the experimenter. 

Trace the cardio-pneumatogram. 

(24) Is there a relation between the rhythm of the 
pulse and the waves of the tracing ? If so, account 
for this relation. 

(25) Account for the essential features of the cardio- 
pneumatogram. 



XXXI. Demonstration: Quantitative determination of 

the C0 2 and H 2 eliminated from an animal 

in a given time. 

i. Appliances. — A four-ounce YVoulff bottle with three 
necks, and with delivery tubes and stopper ground in 
the necks [Fig. 24 a], three five-inch calcium chloride 
tubes, with side tubes and perforated glass stoppers, 
opening and closing the flow of gas [Fig. 24, c, e, f] ; 




Fig. 24. 

Fig. 24. Apparatus for quantitative determination of the carbon 

dioxide gas and water eliminated from an animal in 

a given time. 

Geissler's potash bulbs with CaCl 2 tube ground on (g); 
two small flasks (b, h) with rubber stoppers, double-bored, 
with delivery tubes fitted as shown in the figure; a one 
or two liter bottle with very wide mouth to use as an an- 

140 



RESPIRA TION. 141 

imal cage, fitted with delivery tubes, and with a cork 
impregnated with paraffin; siphon apparatus, as figured, 
consisting of two 8 liter bottles with paraffined corks 
and tubes; analytical balances; laboratory balances 
(correct to 0.01 gm.); drying oven; chemicals, KOH, 
Ba(OH) 2 , CaCl 2 ; any small animal whose weight in 
grammes does not exceed \ the volume of the animal 
cage expressed in cubic centimeters. 
Preparation. 

(1) Fill the calcium chloride tubes; put them into the 
drying oven, where they are to be kept at a tempera- 
ture of 100° to 120° C. for several hours; cool in a des- 
iccator and weigh upon the analytical balances the 
tubes e and f, recording the weight in milligrammes. 

(2) Fill the Woulff bottle and the Geissler's bulbs with 
a strong solution (50% or more) of KOH. Fix into 
position upon the Geissler bulb, its filled and desic- 
cated CaCl 2 attachment, and fit to each end a rubber 
juncture; clamp with strong serre-fine forceps and weigh 
upon the analytical balances. 

(3) Fill the flasks b and h with a strong solution of 
Ba(OH) 2 . These flasks serve simply to show 
whether or not the C0 2 gas has all been absorbed by 
the KOH through which it has just passed. 

(4) Pieces e, f and g should be fixed to a light wooden 
rack, by which they may be moved; if this is not con- 
venient clamp them to supports. 

(5) Join up apparatus a, b and c. 

(6) Fill siphon apparatus. 
(*7) Weigh the animal cage. 

Operation. 

(1) Put the animal into the jar; fix the cover so that it 
will not leak air. 

(2) Join animal cage with c and with siphon appa- 



142 LAB OR A TOR Y G UIDE IN PHYSIO LOG Y. 

ratus. Start the siphon and note the rate of flow 
per minute. The level of the water in the lower bot 
tie should be probably 1 meter below that in the upper 
bottle. Notice whether the animal seems to be respir- 
ing normally; if so, it may be taken for granted, after 
ten minutes, that the ventilation is sufficient. If it 
seems insufficient one has only to increase the differ- 
ence of level in the two siphon bottles. 

(3) Disjoin the animal cage and weigh the cage with 
the contained animal upon the laboratory bal- 
ances. Note the time; join the animal cage in circuit 
again, attaching it to e, and attaching z to h. Start 
the siphon. The greater resistance to be overcome 
will necessitate a greater difference in the level of the 
two bottles in order to ventilate at the same rate as 
before. To test joints put the finger over the distal 
tube of the Woulff bottle (a); if the joints are all right 
the siphon stream will stop after a few moments. When 
the water in the upper bottle is lowered nearly to the 
end of the siphon, clamp the tube joining h to i, set 
the empty bottle upon the floor and the full bottle 
upon the higher level, join the tube on at k and un- 
clamp. This whole change need only occupy a few 
seconds. In the meantime C0 2 has been collecting, 
but it has not been lost. 

(4) It is evident that in the afferent apparatus (a, b and 
c) one has a means of robbing the air of CC> 2 and 
H 2 0, thus furnishing the animal with pure, dry air. 
It is further evident that in the efferent apparatus one 
has a means of collecting absolutely all of the C0 2 
and H 2 given off by the animal during the experi- 
ment. Further the weights before and after will show 
just how much of these excreta have been passed into 
the collecting apparatus. 



RESPIRATION. 143 

(5) Note the time (one hour or more); clamp siphon 
tube; turn the stoppers of e and f, clamp x and y; 
disjoin d and weigh it. 

(6) Weigh e; weigh f; weigh g. 
Observations. 

1) How much has the animal lost in weight during the 
period of observation? 

(2) How much water left the animal cage during the 
period of observation? 

(3) What was the source of this water? 

(4) Did the animal micturate or defecate during the 
time of the experiment? If so, is this to be looked 
upon as a source of error in the experiment? Would 
such an occurrence tend to increase or to decrease the' 
amount of water caught in the CaCl 2 tubes e and f? 
Would it cause a discrepancy between the loss in 
weight of the animal, as determined, and the com- 
bined weight of collected H 2 and C0 2 ? 

(5) How much C0 2 left the animal cage during the 
observation ? 

(6) What is the total amount of H 2 and C0 2 collected? 

(7) Does the amount of these excreta collected equal 
the loss in weight in the animal? What should the 
relation of these two quantities be? Explain in full. 

(8) What is the respiratory quotient? 

(9) Formulate several problems which may be solved 
with this method? 



XXXII. Respiration under abnormal conditions. 

Appliances. — Three small animals, e. g. , mice, rats, 
guinea pigs or squirrels. Three wide- mouthed bottles 
or jars which may be sealed; scales or large balances; 
C0 2 generator; water bath; operating case; dissecting 
boards. 

Preparation. — Determine the weight of each animal. 
Choose a receptacle whose cubic contents is about two to 
three times as many cubic centimenters as the weight of 
animal "a" in grams. Choose second and third recep- 
tacles whose contents represent about 12 to 15 c. c. to 
one gram of animals "b" and "c," respectively. 

Operation. 

I. Preliminary. 

a. Put animal "a" into the small jar "a"; count res- 
pirations; close the jar. 

b. Put animal "b" into jar "b." Before closing count 
respirations; close air-tight. 

c. Fill jar "c" one-third full of water and displace the 
water with C0 2 . Put animal "c" into the jar, tak- 
ing care to allow as little loss of C0 2 as possible; 
close; count respirations. 

II. Post-mortem examination. 

After an animal dies fix it to the dissecting board and 

open the abdominal and thoracic cavities; take great 

care not to cut a large blood vessel; pin the flaps out 

so that all of the organs will be exposed and in place. 

Observations. 

a. Respiration in small closed space. 

(1) Make careful record of number of respirations 

144 



RESPIRA TION. 145 

and general condition of animal "a" in the normal 
state, and at the end of every five minutes after the 
closure of the jar. 

What changes in rate or depth of respiration 
have been noted? 

(2) Note all abnormal signs and symptoms. 

(3) On post-mortem examination record the condi- 
tion of heart, large blood vessels, lungs, liver, kid- 
neys and the general appearance of the tissues. 

(4) Compare the conditions with those found in a 
normal animal, prepared by the demonstrator. 

b. Respiration in a larger closed space. 

(5) Note all symptoms of animal " b " every five min- 
utes after confinement in the jar. 

(6) Make a post-mortem examination; record in de- 
tail the condition of the organs as in the case of 
animal "a." 

(Y) Compare animal "b" with the normal animal. 

(8) Compare animal " b " with animal " a." 

c. Respiration in an at?nosphere of one -third C0 2 

(9) Note all symptoms at intervals of five minutes. 

(10) Compare these observations with corresponding 
ones from animal " a " and animal "b." What are 
your conclusions ? 

(11) Make a post-mortem examination; make a record 
as before. 

(12) Compare appearances in animal "c" with those 
in the normal animal; with those of animal "a;" 
with those of animal "b." 

(13) Make a generalized statement of the facts dis- 
covered in the experiments. 

(14) What is the cause of death when an animal is 
inclosed in a small space? 



146 LAB OR A TOR Y G UIDE IN PHYSIO LOG Y. 

(15) What is the cause of death when an animal is 
inclosed in a large space ? 

(16) Have the relations which you have discovered 
any bearing upon the future development of animal 
life upon the earth? 



XXXHI. Respiration in abnormal media. 

i. Appliances. — Three small animals; three jars or wide- 
mouthed bottles; hydrogen generator; nitrogen genera- 
tor; water bath; potassium nitrite; ammonium chloride; 
operating case; dissecting boards. 

2. Preparation. — Dissolve 66 grammes of ammonium chlor- 
ide in 500 cubic centimeters of water. Dissolve 100 
grammes of potassium nitrite in 500 cubic centimeters of 
water. Prepare a nitrogen generator as shown in the 
figure, using a liter flask. (Fig. 25.) 

j. Operation. 

a. Pour the two solutions into the generator; adjust con- 
ducting tube; heat the mixture in the generator; in a 
few minutes nitrogen gas will be given off from the 
mixture as the result of the following reaction: 

NH 4 Cl+KN0 2 = 2H g O+KGl+N 2 . 
If the jars used by the different divisions are not too 
large the above suggested quantities of the solutions 
will probably supply enough gas for several divisions. 
Put an animal into the jar of nitrogen and close the 
jar. 

b. Fill a jar full of water, displace it with hydrogen 
gas. Put an animal into the jar and close it. 

c. Put an animal into a third jar, confining it with a 
cloth or a sheet of rubber. Join a rubber tube to an 
illuminating gas jet, introduce the end of the tube in- 
to the mouth of the jar; turn the gas on for an instant 
only. After five minutes allow another momentary 
puff of illuminating gas to enter the jar. 

147 



148 



LABORATORY GUIDE IN PHYSIOLOGY. 



Observations. 

a. Respiration in an atmosphere of nitrogen. 

(1) Note all symptoms. 

(2) How do these compare with those of death by 
oxygen starvation ? 

(3) Record post-mortem appearances. 

(4) Compare with previous cases. 

b. Respiration in an atmosphere of hydrogen. 

(5) Note carefully every abnormal appearance and 
symptom. 

(6) Make a record of the post-mortem appearances. 




Fig. 25. 



Fig. 25. Nitrogen generator. 



(7) Compare these with the appearances after death 
by oxygen starvation; by C0 2 narcosis. 

c. Respiration in an atmosphere of one- third illuminating 
gas (C<9+). 

(8) Record all symptoms. 

(9) Record post-mortem appearances. 



RE SPIRA TION. 1 49 

(10) How does death in an atmosphere of CO com- 
pare, as to symptoms, with death in an atmosphere 
of nitrogen ? 

(11) Compare it in turn with other forms of death as 
induced in this and the previous chapter. 

(12) Compare the post-mortem appearances in this 
case with those in preceding cases. 



E. DIGESTION AND ABSORPTION. 



As intimated in the introduction it is taken for granted 
that by the time a medical school has found the conditions 
propitious for the establishment of a laboratory of experi- 
mental physiology, the whole province of chemical physiol- 
ogy will have been occupied by the department of 
chemistry as a legitimate growth of that department. 

The American laboratory of experimental physiology 
will present, almost exclusively, the physical problems of 
physiology. But even where such are the conditions it 
may seem advisable to introduce into a course of lectures 
or recitations on the physiology of digestion a series of 
demonstrations. 

The following exercises in the chemistry of digestion 
and the physics of absorption may be given either as dem- 
onstrations or as laboratory exercises. 

This chapter is not intended as a substitute for any of 
the excellent treatises now used in medical schools, but 
rather as a supplement to them. 

It will be taken for granted that the student has had at 
least one year of chemistry before he enters upon this 
course. 

To give the course which is outlined one will need the 
following appliances, apparatus and reagents. 

150 



DIGESTION AND ABSORPTION. 151 

Appliances : 

a. Glass ware utensils, &c. ; 

10 evaporating dishes, assorted sizes; 
10 filters assorted sizes — 5 cm. to 20 cm; 
100 test tubes 15 cm ; 
10 beakers 30 c.c. ; 
10 beakers assorted — 50 c.c. to 2 L. ; 
10 50 c.c. graduated cylinders; 

4 graduated cylinders- — 100 c.c, 200 ex., 500 c.c, 
1000 c.c 

3 wedgewood mortars (2^, 4 and 1 in. in diameter) ; 
Filter paper; 
Labels ; 
Pig bladders ; 
Thread ; 
Rubber tubing; 
Glass stirring rods ; 

b. Apparatus, 

3 Bunsen burners — -with rubber tubing; 
Filter stand ; 

2 supports with rings and gauze ; 
8 dialyzers 

1 incubator; 
Drying oven ; 
Meat hasher 
Desiccator ; 

3 Water baths ; 

Platinum dish' — 15 c.c. to 100 c.c. 

c. Reagents. 
Diluted iodine ; 
Fehling's solution ; 

Sodium hydrate and potassium hydrate; 
Copper sulphate; 
Distilled water; 



152 LAB OR A TOR Y G UJD E IN PH YSIOL OGY. 

Neutral litmus ; 
Concentrated nitric acid ; 
Strong ammonia ; 
Acetic acid; 
Osmic acid 1 % ; 
Pure standard pepsin ; 

Muriatic acid C. P. (Sp. gr. 1.16 = 31.9 % abs. HC1 ;) 
Absolute alcohol ; 
Ether; 
Chloroform ; 
Calcium chloride ; 
25 % solution NaOH ; 
25 % solution KOH ; 
y 2 saturated solution Na 2 CO s ; 

Nonmedicated absorbent cotton for rapid filtering of 
mucilaginous or albuminous liquids. 



XXXIV. The carbohydrates. 

/. Materials. — Potato starch; dextrin; dextrose; maltose; 

lactose; saccharose; cellulose represented by absorbent 

cotton and ashless filter paper. 
2. Preparation. 

(1) To prepare Fehling 's solution: 

a. Into a half-liter, glass-stoppered bottle put 34.64 
gm. CuS0 4 c.p., and enough H 2 dist. to make 
500 c. c. Label the solution: Fehling 1 s solution (a). 

b. Into a similar receptacle put 173 gms. of potassic- 
sodic tartrate — KNaC 4 H 4 O e -f 4H 2 [Rochelle 
salt] and 50 gm. of NaOH, weighed in sticks; add 
enough water to make 500 c c. Label: Fehling' s 
solution (b). For use mix these two solutions in 
equal parts. A convenient quantity for the follow- 
ing experiments is 50 c. c. of each in 100 c. c. bottle. 

(2) Prepare a starch paste by rubbing 1 gm. of starch to a 
creamy consistence with water, add 100 c. c. of distilled 
water and boil, 

(3) Prepare a dilute solution of iodine by direct solu- 
tion in water or by diluting an alcoholic solution. 

J. Fxperiments and Observations. 

(1) Put a little dry starch into an evaporating dish; add 
some dilute iodine. The starch turns blue. Pour a 
few drops of starch paste into a test tube; add a few 
drops of iodine. Iodine may be used to detect the 
presence of raw or of cooked starch. 

(2) Put some raw starch into a test tube or beaker; add 
water; stir. The starch does not seem to be at all 

153 



154 LAB OR A TOR Y G UIDE IN PHYSIOLOG Y. 

soluble in water. Stir or shake the mixture to bring 
the starch into suspension in the water; pour upon a 
filter. A clear filtrate passes readily through. Test 
the nitrate for starch; result, negative; pour a few 
drops of iodine upon the filter, starch present. Con- 
clusions: 

(#) Potato starch is insoluble in cold water. 

(3) The granules of potato starch will not pass 
through common filter paper. 

(3) Dilute a few cubic centimeters of starch paste; pour 
it upon a filter; to the filtrate add iodine. The blue 
color indicates that in the cooking of starch the grains 
are broken up into particles sufficiently small to readily 
pass through the meshes of common filter paper. 

(4) In order to determine whether dilute starch paste 
will in response to the laws of osmosis pass through 
an animal membrane, fill a dialyzer with dilute starch 
paste. Set aside to be tested one or two days later. 

(5) Put a bit of absorbent cotton into a beaker or test 
tube; add water, boil; add iodine. Cellulose, as repre- 
sented by cotton fibers, is insoluble in water and does 
not respond to the iodine test. 

(6) Put a few bits of ash-free filter paper into a test 
tube; add water; boil; add iodine. Cellulose, as repre- 
sented by the fibers of ash free filter paper, is insol- 
uble in water and responds to the iodine test. One 
must remember in this connection that in the prepa- 
ration of ash-free filter paper mineral acids are used 
to dissolve out the salts; and mineral acids, especially 
sulphuric acid, so modify cellulose that it responds to 
the iodine test with a blue color. 

(7) Add water to dextrin in a beaker; stir with a rod. 
Dextrin is readily soluble in cold water. To a small 
portion add iodine. The solution will probably as- 



DIGESTION AND ABSORPTION. 155 

sume a wine color; the typical reaction of erythro-dex- 
trin. 

(8) Fill a dialyzer with diluted dextrin solution and 
leave for subsequent examination. 

(9) Add water to dextrose; it is readily soluble. Add 
iodine to a portion of the solution; result, negative. 

(10) Fehling's test for a reducing sugar: To a few drops 
of the solution add several cubic centimeters of Feh- 
ling's solution and boil. A yellowish precipitate of 
cuprous oxide (CuO) appears. If the boiling is con- 
tinued the color changes to a brick dust red. 

(11) To a solution of maltose, add Fehling's solution 
and boil; the copper solution is reduced and CuO is pre- 
cipitated. 

(12) To a solution of lactose, add Fehling's solution and 
boil] reduction takes place. 

(13) Subject a solution of saccharose to the Fehling 
test. No reduction occurs. 

(14) Tromer's test for a reducing sugar: To any liquid 
suspected of containing a reducing sugar, add a few 
drops of very dilute CuS0 4 solution; to this mixture, 
add an excess of NaOH (or KOH); boil; if the sus- 
pected liquid contain a reducing sugar, the CuS0 4 will 
be reduced with precipitation of CuO. Subject all 
of the solutions of sugar in turn to the Tromer test. 
Note that the appearance is practically the same as 
with the Fehling test. Any differences are due, not to 
a difference in the essential reaction but to a difference 
in the proportions of the two reagents. The Fehling 
test is more satisfactory. 

(15) Fill a dialyzer with a dilute solution of dextrose for 
subsequent examination. 



156 LABOR A TOR Y GUIDE IN PHYSIOLOG Y. 

(16) Fill a dialyzer with a dilute solution of maltose or 

lactose for subsequent examination. 
(1*7) Fill a dialyzer with a dilute solution of saccharose 

for subsequent examination. 

Questions and Problems. 

(a) How may carbohydrates be classified ? [Make three 
classes.] 

(b) Which class has the lowest grade of hydration? 

(c) How many of this class are soluble in cold water? 

(d) How many are diffusible ? 

(e) Which class has the highest grade of hydration? 

(f) Are all of those which belong to the third class 
soluble in water ? 

(g) Are they all diffusible ? 

(h) How may dextrin be classified ? 

(j) How many of the carbohydrates reduce CuS0 4 in 
presence of an excess of NaOH or KOH ? 

(k) How many of the carbohydrates are diffusible ? 

(1) How may one determine whether or not cane sugar 
passed ihrough the animal membrane ? 



XXXV. Salivary digestion. 

Materials. — Bread; fibrin; pig-fat; olive oil; starch 

paste; cane sugar. 
Preparation. 

Remove the parotid and submaxillary glands of several 
rabbits or rats, hash them; rinse quickly with water to 
remove blood; cover with water. After a few hours 
(12-24) filter or strain off the opalescent aqueous ex- 
tract. It should contain an aqueous solution of ptya- 
lin. Label: Salivary Extract. 

(2) Chew a piece of rubber or paraffin. The flow of 
saliva is stimulated; catch the secretion in a beaker; 
dilute and filter. Label: Salivary Secretion. 

(3) Fibrin for use in experiments on digestion may be 
procured in any quantity at a slaughter house. Rid it 
of all red coloring matter and of accidental contamina- 
tion by repeatedly soaking and washing in water. The 
white, elastic shreds of fibrin may be kept indefinitely 
in pure glycerin. For use one needs only to wash 
out the glycerin thoroughly. 

Experiments and Observations. 

(1) Subject saliva (a) and (o) to the Fehling test. 
It will be found that neither the extract nor the secre- 
tion will reduce the CuS0 4 . 

(2) Subject starch paste to the same test. The result 
is negative. 

(3) Mix equal volumes of starch paste and salivary 
extract in a beaker. Place the mixture in the incu- 
bator, which is kept at a temperature of 35° to 40° C. 

157 



158 LAB OR A TOR Y G UIDE IN PHYSIOL OGY. 

After ten or fifteen minutes subject the mixture to a test 
with Fehling's solution. If the conditions are normal a 
copious precipitate of CuO indicates that a change has 
been wrought in the mixture. The starch has been 
changed to a reducing sugar by the ptyalin of the 
salivary extract. 

(4) Mix equal volumes of starch paste and salivary 
secretion in a beaker, place the mixture in the incu- 
bator for ten or fifteen minutes; test with Fehling's 
solution. The presence of a reducing sugar shows 
that the secretion of the human salivary glands has 
the power to change starch to sugar; to change an in- 
soluble, indiffusible foodstuff to a soluble, diffusible 
one. 

(5) Put a few crumbs of bread into a test tube; add 
dilute iodine. Starch is an important constituent of 
bread. 

(6) Put a few crumbs of bread into a beaker; add 
salivary extract; place in the incubator twenty minutes. 
Disintegration of the pieces and a marked increase of 
the amount of reducing sugar indicates the digestive 
action of saliva upon bread. 

(7) Put a bit of fibrin into salivary extract; place in 
the incubator. An hour or a day will show no appar- 
ent change in the fibrin. Had one used any other 
proteid the result would have been the same. We are 
justified in the conclusion that saliva contains no 
ferment capable of changing proteids. 

(8) Put a bit of fat or a drop of oil into a few cubic cen- 
timeters of salivary extract, shake vigorously; place in 
incubator. After an hour or day one sees no change in 
the fat or oil, and is justified in the conclusion that 
saliva contains no ferment which acts upon fats. 

(9) To a small amount of raw starch add salivary ex- 



DIGESTION AND ABSORPTION. 159 

tract, place the mixture in the incubator; shake fre- 
quently; after fifteen minutes test for reducing sugar. 
There will probably be a relatively small amount of 
reducing sugar. If one watches the progress of the 
digestion for several hours he will be convinced that 
the cooking of starch very greatly facilitates its diges- 
tion by saliva. 

(10) Boil a few cubic centimeters of saliva; add starch 
paste; place in the incubator for ten minutes; test for 
reducing sugar. What is the verdict? 

(11) Test the salivary secretion with neutral litmus. 
Determine whether its faint, alkaline reaction is essen- 
tial to its action as a digestive fluid. 

(a) To one portion of saliva add an equal volume 
of 0.3% hydrochloric acid and the same amount 
of starch paste. The mixture represents 0.1% 
hydrochloric acid. Place the mixture in the 
incubator for fifteen minutes; test with Fehling's 
solution. Verdict ? 

(£) Repeat the experiment substituting, for the 
hydrochloric acid, lactic acid of the same strength; 
place in the incubator for fifteen minutes; test with 
Fehling's solution. 

What is the conclusion ? 

(12) To determine the course of salivary digestion. Mix 
50 c. c. of salivary extract with an equal amount of 
starch paste. Test a portion with iodine at once. 
Test another portion at once with Fehling's solution. 
Keep the beaker in a water bath at blood tempera- 
ture. Test a portion of the mixture every minute 
with iodine and another portion every minute with 
Fehling's solution. 

(a) What is the first change noted in the digestion 
of the starch ? 



1 60 LAB OR A TORY G UIDE IN PH YSIOL OGY. 

(&) How many steps may be made out with the 
means used and under the conditions existing in 
the experiment ? 

(<r) In what order do the changes occur? 

(13) Place some starch paste in a beaker which may be 
floated in ice water; similarly float a beaker with 
saliva. After both liquids have been cooled down to 
near the temperature of the surrounding water, mix 
them in one of the beakers; keep the mixture at the 
low temperature while subjecting portions of it every 
two minutes to the tests suggested above. 

(#) May the same changes be made out in this ex- 
periment as in the previous one? 

(£) Are the changes in the same order ? 

(V) State any differences in salivary digestion at 
blood temperature and at the low temperature 
(0°C) used in this experiment. 

(14) («) Sum up the day's work in a series of conclu- 
sions. 

{/?) What is the chemical formula of starch ? Of 
erythro-dextrin ? Of maltose ? Of dextrose? 

(6-) Write a chemical reaction or a series of reac- 
tions which will be in harmony with the observa- 
tions and show as nearly as possible the course of 
salivary digestion. 

(d) What change has the ferment wrought in the 
starch molecule to render the resulting carbohy- 
drate capable of diffusion through animal mem- 
brane ? 



XXXVL The proteids. 

i. Materials. — An egg; fibrin; gelatine; myosin; syntonin; 
acid albumin; commercial peptone (mixed albumoses, 
proteoses and peptones); Griibler's pure peptone. 

2. Preparation. 

{a) To prepare myosin: 

(1) Take one pound of lean meat, grind it in the meat 
hasher; soak and wash repeatedly until the tissue is 
nearly white and quite free from haemoglobin. 

(2) Put the washed muscle tissue into a flask with an 
equal bulk of a 20% solution of ammonium chloride; 
shake from time to time for 24 hours. 

(3) Strain off the liquor and add to it 20 volumes of dis- 
tilled water. Myosin is precipitated. Wash the pre- 
cipitate. Redissolve one-fourth of the precipitate in 
10% NaCl, and label: Saline Solution of Myosin. 

b. To prepare syntonin. — To the remaining three-fourths 
of the washed myosin add several volumes of 0.1% hy- 
drochloric acid. In a very short time the myosin will 
be dissolved and changed to syntonin. 

c. To prepare dilute egg albumin. — Make an opening in 
one end of the shell of an egg; drain off the white of the 
egg, catching it upon a coarse linen cloth — a towel serves 

"the purpose well; press the albumin through the meshes 
of the linen into a beaker; add 400 or 500 cubic centi- 
meters of distilled water; transfer the mixture to a 1 L. 
cylinder and shake vigorously; after a short time filter 
through pure absorbent cotton or strain through fine 
linen. 

161 



162 LABORATORY GUIDE IN PHYSIOLOGY. 

d. To prepare acid albumin. — To 100 c.c. of dilute egg 
albumin add an equal quantity of 0.2% hydrochlo- 
ric acid; place the mixture in the incubator for two 
or three hours. Though the change begins at once it 
will probably not be complete before the time suggested. 
If one wishes to isolate the acid albumin from the mix- 
ture he has only to carefully neutralize with sodic hy- 
droxide precipitating the acid albumin, and to wash the 
precipitate with distilled water. For the purposes for 
which it is to be used in the following demonstration it 
may be left in the acid solution which represents 0.1% 
HC1. 

Label: Acid Albumin Solution in 0.1% HC1. 
e. — Make an aqueous solution of the commercial "pep- 
tone," and though peptone is present in small propor- 
tion, label it: Proteoses. 

f. Make an aqueous solution of a few grammes of Grii- 
bler's pure peptone, and label: Peptone. 

g. Dissolve a few grammes of gelatin in distilled water. 
h. To prepare MillorCs reagent: 1st. To 100 grammes of 

pure mercury add an equal weight of concentrated 
nitric acid c. p. The reaction proceeds at room 
temperature, though gentle heat may be applied to 
complete the solution of the mercury. 2d. Cool the 
mixture; add two volumes of water; after 12 hours 
decant the supernatant liquid — Milton's Reagent. 
j. Experiments and Observations. 

(1) Pour into test tubes a few cubic centimeters of 
each of the following proteid solutions and subject 
each in turn to a temperature of 57°C, then to a tem- 
perature of 63°C, and finally a temperature of 100°C, 
by dipping the tubes into waterbaths of the tempera- 
tures named: 

(a) Dilute egg albumin. 



DIGESTION AND ABSORPTION. 163 

(£) Saline solution of myosin. 
(<r) Syntonin in acid solution. 
{d) Acid albumin in acid solution. 
(e) Gelatin in aqueous solution. 
(/) Proteoses. 
(g) Peptone. 

Record the results in a table and formulate con- 
clusions. 

(2) Subject the same series of proteids to the cold nitric 
acid test by first pouring one or two cubic centimeters of 
strong nitric acid into a test tube, then with pipette care- 
fully floating the proteid liquid upon it. In the case oi 
dilute egg albumin a characteristic white ring forms 
between the acid and the albumin. Note in each case 
whether or not a typical ring is formed. 

(a) Dilute egg albumin. 

(<£) Saline solution of myosin. 

(V) Syntonin. 

(d) Acid albumin. 

(e) Gelatin. 
(/) Proteoses. 
(g) Peptone. 

Tabulate results and formulate same in a concise 
statement. 

(3) The Xanthoproteic test. 

Use the tubes and materials already prepared in the 
cold nitric acid test. Shake the tubes to mix the acid 
with the proteid. In some cases a coagulum will be 
formed and this coagulum turns yellow on boiling if 
the tube is held in a Bunsen flame. After the coagu- 
lum has been boiled in the acid, cool under the hydrant 
or in a pail of ice water and add strong ammonia to 
alkaline reaction. The light yellow coagulum which 
forms in the case of egg albumin turns to an orangecolor. 



164 LAB OR A TOR Y G UIDE IN PH YSIOL OGY. 

This test is usually given as a universal proteid test. 
Tabulate results on the above suggested series (a)-(g) 
noting any variations of the reaction in the different 
proteids. Besides variations in the reaction with dif- 
ferent proteids there are marked variations with differ- 
ent strengths of solution of the same proteid. 

(4) A general test for proteids is to heat a proteid-con- 
taining liquid with half its volume of Milloris reagent. 
A precipitate appears which is yellowish at first but 
turns red under the influence of heat. Test each of 
the above list of proteids (a-g), with Millon's reagent. 
Record results. 

(5) The Biuret test. 

To a suspected liquid add an excess of sodic hydrate; 
shake well and to the mixture add one or two drops 
of a very dilute solution of cupric sulphate. A violet 
color appears which on heating becomes deeper in 
shade. 

A most convenient reagent for this reaction is a 
mixture of the solutions (a) and (b) of the Fehling's 
test not in equal quantities as in the typical Fehling's 
solution, but in the proportion of nine parts of the 
sodic hydroxide solution (b) to one part of the cupric 
sulphate solution (a) and add an equal volume of dis- 
tilled water to the mixture. 

Tabulate results on the proteid series (a) to (g). 

(6) Subject each of the series of proteids (a) to (g) to 
each of the following reagents tabulating results: 

(I) Picric acid, saturated solution. 

(II) Absolute alcohol. 

(III) Mercuric chloride, saturated solution. 

(IV) Tannic acid, saturated solution. 

(V) Silver nitrate, 10% solution. 

(VI) Ammonium sulphate, saturated solution. 



DIGESTION AND ABSORPTION. 165 

On which of the proteid solutions would one get 
a precipitate with silver nitrate independent of the 
presence of proteid? 

(7) To separate peptone from other proteids. — It will have 
been noted that ammonium sulphate precipitates all 
proteids except pure peptone. If one has peptone 
mixed with proteoses and unchanged proteids one may 
demonstrate its presence by precipitating out the other 
proteids and then demonstrating by such a test as the 
Biuret test the presence of a proteid in the clear fil- 
trate; that could be nothing else than peptone. 

Test commercial peptone in this way and determine 
whether any appreciable proportion of it is peptone. 

(8) The diffusibility of proteids. — Fill seven dialyzers 
with the proteids above studied. 

On the following day test the diffusates for proteids. 



XXXVII. a. Diffusibility of proteids. 
b. Milk. 

a. Diffusibility of proteids. 

1. Materials. — The seven dialyzers filled at the end of 
the previous demonstration. 

2. Experiments and Observations. 

( 1 ) What reagent may best be used to determine whether 
or not any of the egg albumin has diffused through the 
animal membrane? 

(2) How may one determine whether or not any of the 
salts of the egg albumin have diffused through the 
membrane? 

(3) In the case of the saline solution of myosin (b), of 
syntonin (c) and of acid albumin (d), is there any con- 
traindication against silver nitrate as a reagent to 
determine whether proteid has diffused? 

What would silver nitrate indicate in this case ? 

(4) What tests would be most reliable in these cases to 
detect the presence of proteid in the diffusate ? 

(5) Would a trace of proteid in the diffusate necessarily 
demonstrate the diffusibility of these proteids through 
the walls of the alimentary tract ? If not; why not ? 

(0) What tests may be used to determine the presence 
of gelatin in the diffusate ? Is gelatin diffusible ? 

(7) The term proteoses is a general one and is used to 
designate the mid-products of proteid digestion. The 
mid-product of albumin digestion is albumose; of 
globulin digestion, globulose; of myosin, myosinose; 
of vitellin, vitellinose; of casein, caseinose; or in gen- 
eral of a proteid, proteose. 

166 



DIGESTION AND ABSORPTION. 167 

Dialyzer (f) contains products of peptic digestion 
of proteids — principally albumin. The progress of 
digestion was suspended at a stage when there were 
present not only peptone but mid-products — albu- 
moses; or, to use the general term, proteoses 

The problem which confronts us is — to determine 
whether or not proteoses are diffusible. 

(a) If peptone is diffusible the diffusate will cer- 
tainly contain peptone. Do peptone and the pro- 
teoses respond alike to all the general tests for 
proteids? 
(b.) How may peptone be separated from the pro- 
teoses ? 

What single reagent is indicated in the case? 
(8) Demonstrate the diffusibility of peptone. 
b. Milk. 
/. Materials. — One liter of fresh whole milk; one liter of 

milk for the preparatory steps of the demonstration. 
2. Preparation. 

(1) On the day before the demonstration fill a 500 c. c. 
open mouthed cylinder with milk and put it in a cool 
place. 

(2) Two days before the demonstration weigh out 10 
gm. to 50 gm. of whole milk in a platinum dish or in 
a thin porcelain dish. Place it in a drying oven at 
90°-95°C, and dry to constant weight. Record the dry 
weight. 

(3) Before the hour of the demonstration burn the resi- 
due by bringing the dish which contains the dry solids 
to a red glow in a Bunsen flame, allowing ample access 
of oxygen. After the dish and the white ashes have 
cooled in a desiccator take the weight. All of these 
weights should, of course, be taken upon an analytical 
balance. 



168 LABORATORY GUIDE IN PHYSIOLOGY. 

(4) Fill a dialyzer with diluted milk one day before the 
demonstration. 
J. Experi?nents and Observations. 

(1) What proportion of milk evaporates at the tempera- 
ture above suggested ? It may be taken for granted 
that this proportion represents practically the water 
of the milk. 

(2) Of the solids of milk what proportion is organic and 
what proportion is inorganic? 

(3) What bases predominate in the ashes? [Let a 
student be assigned this problem for solution.] 

(4) What is the character of the organic constituents of 
milk? 

(a) Note that the milk that has been standing has 
separated into two layers, an upper yellowish layer 
and a lower bluish white layer. 

(b) Draw off with pipette a few cubic centimeters of 
the cream and in a test tube add an equal volume of 
osmic acid. To a few drops of olive oil in another tube 
add osmic acid. Shake both tubes vigorously. Osmic 
acid has the same effect upon the cream as upon the 
olive oil. The cream is, in fact, fat in physiological 
emulsion. Quantitative examination shows that 
about 4% of milk or 4-13 of the solids of milk con- 
sists of fats in which olein predominates. 

(5) Fill a siphon with water and introduce it through 
the cream to the bottom of the 500 c.c. cylinder; draw 
off 300 c. c. of the milk; add to it four volumes of 
water; slowly add \°J acetic acid while stirring with a 
rod, until the casein separates as a copious flocculent 
precipitate. After the casein has partially settled de- 
cant off a few cubic centimeters of the supernatant 
liquid and subject it to the Fehling test. The abun- 
dant precipitate indicates the presence of a reducing 



DIGESTION AND ABSORPTION. 169 

sugar. It is milk sugar — lactose. About 4.4% of 
milk or x /z of the solid matter of milk is lactose. 
(0) Wash the casein by the repeated addition of water, 
followed by decantation; pour it into a linen sack 
or a towel and press out the water; further extract 
the water with absolute alcohol; extract the remnant 
of fat with ether; dry in the air. The white granular 
material that remains is nearly pure casein, the most 
important proteid of milk, and represents nearly 4% 
of milk. 

(7) Heat 100 c. c. of the fresh milk in a beaker. Before 
the boiling point is reached a membrane gathers upon 
the surface of the milk. This membrane represents 
the lact-albumin of the milk, which has been coagu- 
lated by the heat and has collected in the membranous 
coagulum at the surface. The lact-albumin repre- 
sents only a small proportion of the milk proteid. 

(8) To 30 c. c. of fresh milk in a beaker add common 
salt to saturation. Record results. 

(9) To 30 c.c. of fresh milk in a beaker add magnesium 
sulphate to saturation. Record results. 

(10) Dilute fresh milk to one-fifth normal and subject it 
to the following tests, recording results: 

{a) The iodine test. 

(£) Tromer's test. 

(V) The xanthoproteic test. 

(d) The Biuret test. 

(>) The picric acid test. 

(/) The absolue alcohol test. 

(g) The osmic acid test. 

(11) Fill a dialyzer with the diluted milk. One day 
later examine the diffusate: 

{a) For any of the inorganic constituents of milk. 
(b) For the carbohydrate constituents of milk. 



170 LABOR A TOR Y G UIDE IN PHYSIOL OG Y. 

(c) For the proteid constituents of milk. 

(d) For the fatty constituents of milk. 

(12) Formulate in a series of concise statements the 
facts demonstrated regarding milk: 
{a) Its chemical constituents. 
(£) Its physical properties. 
Why should milk be discussed in connection with the 
proteids rather than with the carbohydrates; considering 
that the proportion of carbohydrate in milk is greater than 
that of proteid? 



XXXVIII. Gastric digestion. 

Materials.— Two fresh pig-stomachs; T / 2 Ko, clean sea 
sand; 4 eggs; fibrin; bread; milk; jellied gelatin; casein; 
rennin. 
Preparation. 
( 1 ) To prepare artificial gastric juice. 

(a) Stretch a fresh stomach of a pig upon a board 

with mucous surface up; fix with nails. 
(£) Rinse off the mucous membrane gently with cold 

water. 
(c) Scrape thoroughly with a dull edged table knife, 
or an equivalent; collect the scrapings in a large 
mortar. 
(«T) Grind the scrapings in clean, fine sand. 
(<f) Add an equal volume of 0.2 r / c HC1 and leave for 

24-48 hours, stirring occasionally. 
(/) Strain through linen; filter, and preserve in a glass 
stoppered bottle. Label: Acidulated aqueous extract 
of pepsin, 
(g) For use dilute this extract with three or four vol- 
umes of 0.1%, HC1 (App. A-1T). Label: Artificial 
gastric juice (1). 
v2) To prepare a glycerin extract of pepsin. 

(a) Rinse off the mucous membrane of a fresh pig- 
stomach with cold water and remove the mucous 
membrane from the muscular walls of the stomach. 
(£) Grind the mucous membrane in the meat hasher. 
(c) Put the hashed tissue into a beaker and cover 
with two volumes of pure glycerin. Stir the mix- 

171 



172 LABOR A TOR Y G UIDE IN PHYSIOLOG Y. 

ture occasionally for several days. The glycerin 
extracts the pepsin ferment. 

(d) Strain the glycerin extract through fine linen; 
preserve in a glass stoppered bottle for future use. 
It will keep indefinitely. 

(e) For use add to 1 volume of the extract 30 to 50 
volumes of 0.2% HC1. Label: Artif. gast. juice (2). 

j. Experiments and Observations, 

(1) To a bit of starch paste of the consistency of jelly 
add artificial gastric juice (1); place in the incubator; 
in ten minutes or one day note results. Results? 

(2) To a few drops of olive oil or to a bit of pure 
tallow add several cubic centimeters of gastric juice 
and keep at incubator temperature for a day. What 
effect has gastric digestion upon fat or oil ? 

(3) To a bit of pig fat add gastric juice and keep at 
incubator temperature for several hours. What 
effect has gastric digestion on adipose tissue ? 

(4) To a bit of fibrin in a test tube add gastric juice. 
The warmth of the hand will be sufficient. If the 
preparation of artificial gastric juice has been suc- 
cessful, the fibrin will dissolve in one or two min- 
utes. One may be certain that digestion is pro- 
gressing rapidly, though complete solution of the 
fibrin does not necessarily indicate complete diges- 
tion of it; for complete digestion of a proteid im- 
plies that the food stuff in question is both dissolved 
and diffusible. The fibrin is dissolved, it may or 
may not be diffusible. But this will be determined 
later. 

(5) To determine the active factors of gastric digestion, 
{a) To a few shreds of fibrin in a test tube add a 

few cubic centimeters of 0. 2 % HC1. Carefully note 
results. Will dilute HC1 dissolve fibrin? Is it 



DIGESTION AND ABSORPTION. 173 

possible to digest a proteid without dissolving it? 
(J>) To fibrin add dilute neutral glycerin extract of 

pepsin. Is solution affected ? 
(c) To tube (a) add a few drops of the glycerin extract 
of pepsin. 

To tube (b) add 2 volumes of 0.2% HC1. 
Note results. 
{ct) Formulate conclusions. 
(6) To deter?nine whether the acid factor of gastric diges- 
tion need necessarily be hydrochloric acid. 

Prepare a 0.4% solution of each of the following 
acids: 

(I) Lactic acid. 

(II) Sulphuric acid. 

(III) Nitric acid. 

(IV) Phosphoric acid. 

(V) Citric acid. 

(VI) Acetic acid. 

For each acid prepare four test tubes as follows: 
(I) Lactic acid. 

{a) Fibrin -|- 1 c. c. glyc. ext. of pepsin -f- 10 c. c. 

0.4% acid. 
(o) Fibrin +1 c. c. pepsin ext. -f- 10 c. c. 0.2% 

acid. 
(<:) Fibrin -f- 1 c. c. pepsin ext. + 10 c. c. 1% 

acid. 
(d) Fibrin -4- 1 c. c. pepsin ext. -|- 10 c. c. 0.05% 

acid. 

Proceed in a similar manner with each acid. 
Tabulate results. May any other acid or acids 
take the place of HC1 as a factor in digestion? 
If so, in what minimum strength? Which one of 
the above acids may be normally present in the 



174 LAB OR A TOR Y G U1DE IN PHYSIOL O G Y. 

stomach? May any of the above acids serve as 
digestives and as foods? 

As digestives and as tonics? 
As digestives, foods and tonics? 
Cite authorities. 
(7) To deter 'mine the optimum strength of the hydro- 
chloric acid. 

Prepare with care the following three dilutions of 
hydrochloric acid: 10%, 1%, 0.1%. [See Appendix 
A, 17.] 

Into twelve test tubes put as many small masses 
of fibrin; into each tube put 1 c. c. of neutral 10% 
dilution of glycerin extract of pepsin. Label and fill 
tubes as follows: 
Tube (a) 5%: Add to the fibrin 5 c. c. of 10% HC1 

and of distilled water a quantity sufficient to make 

10 c. c. 
Tube (b) 2%: Add 2 c. c. of 10% HC1 and aqua dist. 

q. s. ad 10 c. c. 
Tube (c) 1%: Add 1 c. c. of 10% HC1 and aqua dist. 

q. s. ad 10 c. c. 
Tube (d) 0.5%: Add 5 c. c. of 1% HC1 and aq. dist. 

q. s. ad 10 c. c. 
Tube (e) 0.4%: Add 4 c. c. of 1% HC1 and aq. dist. 

q. s. ad 10 c. c. • 
Tube (H 0.3%: Add 3 c. c. of 1% HC1 and aq. dist. 

q. s. ad 10 c. c. 
Tube (g) 0.2%: Add 2 c. c. of 1% HC1 and aq. dist. 

q. s. ad 10 c. c. 
Tube (h) 0.1%: Add 1 c. c. of 1% HC1 and aq. dist. 

q. s. ad 10 c. c. 
Tube (j) 0.05%: Add 5 c. c. of 0.1% HC1 and aq. dist. 

q. s. ad 10 c. c. 



DIGESTION AND ABSORPTION. 175 

Tube (k) 0.025%: Add 2.5 c. c. of 0.1% HC1 and aq. 

dist. q. s. ad 10 c. c. 
Tube (J) 0.01%: Add 1 c. c. of 0.1% HC1 and aq. dist. 

q. s. ad 10 c. c. 
Tube (m) 0.005%: Add y 2 c. c. of 0.1% HC1 and aq. 

dist. q. s. ad 10 c. c. 

Place these twelve tubes in the incubator and note 
conditions every 10 minutes for the first hour, every 
hour for the first six hours and then at the end of one 
or two days make the final observations. 

Tabulate results. Formulate conclusions. What 
range of strength may, from the experiments with 
artificial gastric juice under artificial conditions, be 
considered the optimum strength for the acid? Is 
there any reason to doubt that the optimum strength 
as determined above is essentially different from the 
optimum strength in normal digestion ? 
(8) To deteri?iine how dilute the pepsin may be and still 
be efficient in digestion. 

This experiment requires a standard solution of 
pepsin to use as a basis. The U. S. Pharmacopoeia 
(p. 295 of the 7th Decennial Revision) gives the fol- 
lowing formula for a standard solution of pepsin: 
Hydrochloric acid (absolute), 0.21 gm. 
Pepsin (pure), 0.00335 gm. 
Water (distilled), q. s. ad 100 c. c. 

The following suggestions are made as to method 
of preparation: To 294 c. c. of water add 6 c. c. of 
dilute hydrochloric acid: — Sol. A.* 

In 100 c. c. of Sol. A. dissolve 0.06*7 gm. of standard 
pepsin : — Sol. B. To 95 c. c. of Sol. A at 40°C. add 5 c. c. 

*HC1. DIL. contains 10$ of Abs. HC1. The C. P. muriatic acid of 
standard Sp. Gr. contains 31.9$ Abs. HC1. 



176 LAB OR A TOR Y G UIDE IN PHYSIOLOG V. 

Sol. B. The resulting mixture is a standard artificial 
gastric juice of the formula given above, and has the 
power of completely digesting at 38°-40°C one-fifth its 
weight of coagulated egg albumin in six hours.* 

From a standard gastric juice prepare the following 
dilutions using 0.1% HC1 as a diluent. It is scarcely 
necessary to say that the greatest care should be 
taken, (1) to make all measurements with preci- 
sion; and (2) to thoroughly shake each dilution before 
drawing off the material for the next lower dilution. 
(a) Standard artificial gastric juice 10 c. c. -f- 1 c » c - 

moist fibrin. 
(£) fa standard artificial gastric juice 10 c. c.-f-l c. c. 

moist fibrin. 
00 lio standard artificial gastric juice 10 c. c.-f-l 

c. c. moist fibrin. 
00 ToVo standard artificial gastric juice 10 c. c. + l 

c. c. moist fibrin. 
00 toyooo standard artificial gastric juice 10 c. c.-j-l 

c. c. moist fibrin. 
(/) toyooo standard artificial gastric juice 10 c. c.-f- 

1 c. c. moist fibrin. 
00 t.ooo.ooo standard artificial gastric juice 10 c. c.-f- 

1 c. c. moist fibrin. 

Keep tubes in incubator or water bath at 38°-40°C. 
Note (1) time required to dissolve fibrin completely, 
(2) time required to change all acid albumin to pro- 
teose or peptone. Will one-millionth standard gastric 
juice digest fibrin at all? Will a lower dilution (one 
ten-millionth) digest it; if so, how dilute, and how 
long a time is required? 



*For details of testing standard gastric juice see Pharmacopoeia. 



XXXIX. Gastric digestion, continued. 

Experiments and observations, continued. 

(9) To determine the influence of the hydrochloric acid of the 
gastric juice upon putrefaction in the stomach. — It has been 
determined that the hydrochloric acid in the stomach 
destroys, under favorable conditions, at least the non- 
pathogenic forms of bacteria. Let us determine the 
strength of acid necessary to destroy the common bac- 
teria of putrefaction. To each tube used in experiment 
(7) add a minute drop of any putrefying fluid. If the 
contents of a tube serve as a good culture field any drop 
of the fluid may be found to be swarming with bacteria 
within a few hours. Within a few hours after infect- 
ing the tubes examine under high power — 700 to 1000 
diameters— a drop of the contents of each tube. 
While making the observations take care not to 
contaminate one tube with the contents of another. 
That the tubes containing 5% or 2% or 1% hydro- 
chloric acid will be found to be free from bacteria goes 
without saying. Just how weak may the acid be and 
destroy the bacteria? How weak may the acid be and 
retard their development? Could one readily drink 
enough liquid at a meal to change the stomach from a 
sterilizing field to a culture field for the bacteria of 
putrefaction ? 

(10) To determine the influence of neutral salts upon diges- 
tion. — Make a saturated aqueous solution of common 
salt; also \ sat. sol, and T ^ sat. sol. 

O) To 8 c.c. of NaCl sat. sol. add 1 c.c. of a 1% 
177 



178 LAB OR A TOR Y G UIDE IN PHYSIOL O G Y. 

HO, and 1 c.c. glyc. ext. of pepsin; put the mix- 
ture into a test tube; label: NaCl sub. saturated. 
Drop in a bit of fibrin and put into the incubator. 
Take six test tubes, provide each with a bit of 
fibrin; label and fill each as follows: 

(b) I Sat. NaCl : — 5 c.c. artif. gast. juice -f- 5 c.c. 
NaCl sat. 

(7) J Sat. NaCl : — 6 c.c. artif. gast. juice + 2 c.c. 
NaCl sat. 

(d) I Sat. NaCl : — 5 c.c. artif. gast. juice -\- 5 c.c. 
NaCl i sat. 

(e) y'g Sat. NaCl : — 6 c.c. artif. gast. juice -f- 2 c.c. 
NaCl \ sat. 

(/) 3V Sat. NaCl : — 5 c.c. artif. gast. juice + 5 c.c. 
NaCl T \ sat. 

(<£") "bt S at - NaCl : — b c.c. artif. gast. juice + 2 c.c. 
NaCl T V sat. 

What fraction of saturation with table salt stops 
proteid digestion ? Explain its action. How 
much NaCl per litre would that represent ? Has 
this any hygienic bearing? 

(11) The effect of mechanically confining the fibrin to pre- 
vent its swelling. — Tie a small mass ot fibrin rather 

• tightly with several turns of white thread; drop it into 
a test tube containing artificial gastric juice; put the 
tube into the incubator and watch results. 

How long a time is required to digest the fibrin? 
Has this any hygienic significance ? 

(12) The influence of division upon the time required to 
digest proteids. — Boil an egg five to ten minutes; cool 
quickly; separate the hard coagulated white from yolk 
and envelopes. 



DIGESTION AND ABSORPTION. 179 

[a) Cut out a one centimeter cube and put it into a 

beaker with 40 c c. artificial gastric juice. 
(J>) Put into a second beaker of 40 c.c. gastric juice 
a centimeter cube which has been divided into 
eight half-centimeter cubes. 
(Y) Prepare another beaker in which are 16 quarter 
centimeter cubes in 10 c.c. of artificial gastric juice. 
(d) Into another beaker with 10 c. c. artificial gastric 
juice put J of a cubic centimeter of the egg albu- 
min which has been finely divided by pressing 
through a fine sieve. 

Note time required in each case to completely 
digest the albumen. 

Has this any hygienic bearing? 
(13) The influence of temperature upon the time required to 
digest proteids. — Prepare five tubes by first providing 
each with 5 c.c. of artificial gastric juice; treat the 
several tubes as follows: 

(a) Bring to 60°C. in water bath; add fibrin; note 

time. 
{b) Bring to 50°C. in water bath; add fibrin; note 

time. 
(V) Bring to 30°C. in incubator; add fibrin; note 

time. 
(</) Leave at room temperature (20°C); note time. 
(<?) Bring to 0°C. in ice water; add fibrin; note time. 
What is the optimum temperature? 
Is the progress of digestion materially retarded 
by a reduction of the temperature ? 

Would the temperature of the stomach contents 
be essentially lowered by the occasional sipping 
of an iced beverage during a meal? 

What is the hygienic significance of the experi- 
ment ? 



XL. Gastric digestion, continued. 

Experiments and Observations, conti?iued. 

(14) The steps of gastric digestion. 

Boil an egg 5 to 10 min.; cool quickly; separate out the 
white; press it through a fine sieve; put into a beaker 
with 100 c. c. artif. gastric juice, and place the beaker 
in a water bath at 40°C. At intervals of 2 minutes for 
the first 10 minutes; then at intervals of 5 minutes for 
the next 20 minutes; then at intervals of 10 minutes 
forthe second half hour and after that at intervals of one 
hour, subject the liquid to tests for egg albumin; for 
acid albumin; for albumose; for peptone. In what order 
and after what length of time do the several products 
appear ? Is the one that is first to appear also first to 
disappear ? 

(15) The artificial digestion of various proteids. 

(a) To a small mass of jellied gelatin add 10 to 15 
volumes of artif. gast. juice, and note effect. 

(^) Subject bread to the xanthoproteic test. The 
presence of proteid material is demonstrated. Put 
a small piece of dry bread into a beaker with gastric 
juice, and note effect. 

(c) Note the course of casein digestion., 

(d) Triturate in a mortar well cooked lean meat; di- 
gest with gastric juice. 

(e) Try the xanthoproteic test upon cooked beans or 
peas; proteid is present. Triturate in a mortar; di- 
gest. 

(/) In each case, demonstrate the ultimate appear- 
ance of peptone. 

180 



DIGESTION AND ABSORPTION. 181 

(16) The artificial digestion of milk. 

Of fresh milk take three portions of 5 c. c. each. 

(a) To one portion add 10 volumes of artif. gast. 
juice; and place it in the incubator at 38° — 40°C. 

(o) Prepare another beaker in the same way but 
place it in a water bath at 38° — 40°C. and keep the 
mixture well stirred, dividing the casein coagulum 
as fine as possible. 

(<:) Place the third portion of milk in the water 
bath. When it has become warm add a few centi- 
grams of rennin. Fifteen minutes later add artif. 
gast. juice. Stir as in (b.) In which of the first 
two does digestion seem to progress the more rap- 
idly? Does the progress or process of the digestion 
seem to be materially different in the last two ex- 
periments, (b) and (c) ? Have any of the obser- 
vations made on milk digestion any hygienic sig- 
nificance ? 

(17) The diffusibility of the products of the artificial 
digestion of proteids. 

From the products of digestion in experiments 
(16-b) digested milk, (15-a) digested gelatin, (15-b) 
digested bread, and (12 d) digested egg albumun, fill 
four dialyzers — first neutralizing the acid with sodic 
carbonate. After 12-24 hours, test the diffusate for 
peptone. Why neutralize the liquid before filling the 
dialyzer ? 

Have all of these indiffusible proteids been wholly 
or in part changed to diffusible peptones by the action 
of the artif. gast. juice? 



XLI. The properties of fats. 

Materials. — Olive oil; cream; butter; beef tallow; lard; 
adipose tissue; cotton seed oil. 
Experiments and Observations. 

(1) The osmic acid test. — Place in test tubes a small 
amount of each of the above food stuffs; add to each a 
few cubic centimeters of osmic acid. A characteristic 
reaction takes place, the result of which is a deep 
brown coloration of the fat. If the conditions are 
favorable the stain deepens into a sepia black. The 
cream and the adipose tissue have proteid admixtures; 
note the variation of the reaction. 

(2) The solubility of fats and oils. — Prepare three tubes 
each of olive oil, of cream, and of tallow; treat each 
material with absolute alcohol, with ether and with 
chloroform. It will be found that all of these re- 
agents are solvents of fats and oils. The alcohol, 
however, dissolves very much more of the oil or fat 
when warm than when cold, as may be demonstrated 
by making the alcoholic solution with the tube im- 
mersed in boiling water; after the alcohol seems to 
have reached the limit of solution at that temperature, 
immerse the tube in cold water. A large part of the 
dissolved oil instantly separates out, but v/ill readily 
redissolve on again immersing the tube in the boiling 
water. 

(3) The saponification of fats and oils. 

{a) To about 2 c. c. of olive oil in a test tube add 1-2 
volumes of a 25% solution of sodic hydrate. Shake 
the mixture vigorously; it is evident that a chemical 
reaction is in progress. The fat is undergoing the 

182 



DIGESTION AND ABSORPTION. 183 

process of saponification. A complete and typical 
saponification requires a more careful apportion- 
ment of the amount of oil and of alkali used and an 
application of heat. 

(£) Repeat the experiment substituting a 25% solu- 
tion of potassic hydrate. The result is similar. 

(7) What is the chemical formula of palmitin? Of 
stearin? Of olein ? 

(a 7 ) What is the chemical formula of palmitic acid? Of 
stearic acid? Of oleic acid? 

(e) Write generalized formulae for each of these acids. 

(3) Write the reaction which takes place in saponifica- 
tion of palmitin; of olein. Note the ready solubil- 
ity of the products of this reaction in water. 

(4) To a solution of soap add any aqueous solution of a 
calcium salt soluble in water, e. g., calcium chloride — 
a curdy white precipitate separates out. Write the 
formula of the reaction. 

May the reaction have any relation to hygiene or 
therapeutics ? 

(5) The emulsification of oils. —Gould defines an emulsion 
as " water or other liquid in which oil in minute sub- 
division of its particles is suspended." One may add, 
more or less permanently suspended. For, if one shake 
together vigorously 2 c. c. of oil with an equal amount 
of water in a test tube he is able to bring about a 
minute subdivision and temporary suspension of the 
oil in the water. While the oil is in this temporary 
physical condition it has the white color typical of 
emulsions in general. In a few minutes, however, 
the particles, as they rise to the top of the liquid 
coalesce into minute globules; then into larger and 
larger globules and finally into a homogeneous, super- 
natant oil-layer. 



184 LABOR A TOR V GUIDE IN PHYSIOLOGY. 

(a) Add to the mixture above described 2 or 3 c. c. of 
strained egg albumin; shake vigorously. One ob- 
serves the same minute subdivision of the particles, 
but they show no tendency to coalesce on standing; 
the suspension is "more or less permanent." 

Why do not the particles coalesce? In what 
respects is this emulsion unlike milk? 

(£) To 2 c. c. of olive oil add 2 c. c. of sirupy solution 
of any gum, e. g., gum acacia; shake the mixture 
thoroughly. An emulsion will be formed. What 
characteristics has this emulsion in common with 
emulsion (a) ? 

(V) To 5 c. c. of cotton seed oil containing a little free 
fatty acid add 10 drops of strong sodium carbonate 
solution and shake. A good stable emulsion is 
made in this way. [Long's Chemical Physiology, 
p. 63.] 

In what way is this emulsion different from those 
which precede ? Which one of the emulsions given 
above is most like the emulsions formed in the small 
intestine? 

(d) What matters present in the small intestine tend 
to promote emulsification of fats ? 
(0) The diffusibility of I at s or their derivatives or modifica- 
tions. 

Fill five dialyzers as follows: 

O) Milk. 

(£) Solution of soap. 

(c) 10% glycerine. 

(d) Emulsion (5-a). 
(<?) Emulsion (5-c). 

Complete the observations on the following day, deter- 
mining what derivations or modifications of fat or oil are 
diffusible. How may the presence of soap in the dif- 
fusate be determined ? 



XLII. Intestinal digestion. 

/. Materials. — 2 pig pancreases; 200 c. c. of pig or ox 

bile. 
2. Preparation. 

(1) Aqueous pancreatic extract (a). 
(a) Free a pig pancreas of fat. 
(£) Grind it in a meat hasher. 
(V) Extract with water kept at a temperature of 25° 

to 28° C. 
(d) After two hours strain through linen and filter 
through absorbent cotton. 
( 2 ) Glycerin extract of the pancreatic ferments, 
(a) After freeing the gland of fat, grind it. 
(o) Place it in two volumes of absolute alcohol for two 

days. 
(V) Drain off the alcohol and transfer to 2 volumes of 

pure glycerin. 
(d) After one week press out the glycerin, which has 
extracted the ferments. 

This glycerin extract will keep indefinitely. To 
make artificial pancreatic juice proceed as follows: 
(<f) To 1 volume of the glycerin extract add 5 or 6 
volumes of water and sufficient sodium carbonate 
solution to give the mixture a distinctly alkaline 
reaction. 
(3.) Preliminary experiments on bile. — This secretion may 
be easily procured from the slaughter house at almost 
any time in the year, whereas the gastric juice and 
pancreatic juice may only be obtained by resort to 
185 



186 LABORATORY GUIDE IN PHYSIOLOGY. 

operative procedures not properly in the field of this 
chapter.* 

(a) To diluted bile add dilute acetic acid. The 
copious yellow precipitate is mucin. 

(b) To diluted bile add absolute alcohol; mucin is 
precipitated; filter. To one portion of filtrate add 
HC1. The yellow precipitate is glycocholic acid. 

" To the other portion of the filtrate add lead 
acetate, which throws down lead glycocholate. 
Remove this by filtration, and to the filtrate add 
solution of basic lead acetate, which gives a further 
precipitation of lead taurocholate." — [Chemical 
Physiology, Long, p. 119.] 

(V) Ginelin's test for bile pigments. — To a few cubic 
centimeters of strong nitric acid in a test tube care- 
fully add dilute bile. At the junction of the liquids 
a play of colors, green, blue, violet, red and yellow, 
will be noted; the green being next to the bile and 
the yellow next to the acid. This delicate and most 
reliable test may be applied to any liquid suspected 
of containing bile. 

(d) The reaction of bile is found to be distinctly 
alkaline. 
J. Experiments and Observations. 

a. The action of pancreat;.: juice upon foods. 

(1) To raw or cooked starch add in one beaker 
aqueous extract of pancreas (a); in another add 
artificial pancreatic juice (b); place the mixtures in 
the incubator; after a short time test for reducing 
sugar. 



*For description of operationsfor the establishment of gastric fistulae, 
bilary fistula? and pancreatic fistulae, see Hand-book for Physiological 
Laboratory, Sanderson, pp. 475-517. 



DIGESTION AND ABSORPTION. 187 

Pancreatic juice contains an amy lo lytic ferment. 

(2) Subject fibrin to the action of both of the pancre- 
atic preparations. 

Pancreatic juice contains a proteolytic ferment. 

(3) Boil fresh milk and mix it with an equal bulk of 
the aqueous extract of pancreas and put the mixture 

• into the incubator. Put also into the incubator 

boiled milk diluted with an equal volume of distilled 

water. The milk which is mixed with pancreatic 

juice will curdle much sooner than the other. 

Pancreatic juice contains a milk curdling ferment. 

(4) Mix 5 or 6 c. c. of neutral olive oil with an equal 
volume of aqueous extract of pancreas; shake the 
mixture vigorously. 

No emulsion is formed. Place one-half of the 
mixture in the incubator. After a few hours any 
undigested oil may be emulsionized on shaking, or 
fresh oil may be emulsified. Explain. 

(5) To the second part of the mixture add 3 c. c. bile; 
shake the mixture vigorously. A good emulsion is 
formed. How is this emulsion formed? What 
factor of an emulsion does the bile add ? What is 
the relation of experiment (5) to experiment (4)? 

Pancreatic juice contains a fat-splitti?ig fen?ient 
whose action liberates fatty acids. 

(6) To starch paste add several volumes of dilute 
bile. Result? 

^7) To fibrin add dilute bile. Result? 

(8) To oil which contains free fatty acid add bile; 
shake the mixture vigorously; Result? 

(9) To neutral oil add bile; shake the mixture vigor- 
ously. What is the result? Allow the mixture to 
stand in the incubator. After several hours shake 
the mixture. 



1 88 LAB OR A TOR Y G UID E IN PHYSIOL OGY. 

Is an emulsion formed? 
(10) Summarize the results of the foregoing experi- 
ments, formulating a series of conclusions regarding 
the action of pancreatic juice; the action of bile and 
their combined action on each class of food. 



XLIII. Absorption. 

Physiologists have entertained the hope that all the 
phenomena of absorption of diffusible substances could 
be eventually explained by the laws of physics. That 
hope has practically given place to the conviction that 
however important it may be to the animal economy to 
produce, in its digestive processes, diffusible products, 
these products do not pass through the epithelial lining 
of the alimentary tract at the rate or in the proportions 
that would be observed in the dialyzer. This need oc- 
casion no surprise; in one case we have to deal with 
living, active cells, in the other with dead tissue. 

Living ceils of muscle-tissue or of gland-tissue have the 
power of selecting from the tissue plasma such materials as 
are needed for the replenishment of their substance. Not 
only does the animal select what shall be taken into the 
alimentary tract but the epithelial lining of that tract 
seems to select what shall be absorbed and to absorb it ac- 
cording to laws which conform only in a most general way 
or which may not conform at all to the laws of osmosis. 
In order, however, to understand the current literature on 
the subject of absorption it is necessary to be familiar with 
the terminology and laws of osmosis and dialysis. To 
that end the student may profitably perform for himself a 
few simple experiments preliminary to more complex ones 
which the demonstrator may suggest or may perform for 
the class. 

/. Appliances and Materials. — Six dialyzers complete, in- 
cluding outer receptacles and supports; 2 or 3, 100 c. c, 

189 



190 LABORATORY GUIDE IN PHYSIOLOGY. 

evaporating dishes; distilled water; sodium chloride; 

alcohol; egg; mercury manometer. 
2. Preparation. 

(1.) Fit four of the dialyzers with membrane of pig- 
bladder. The bladders should be carefully selected as 
to uniformity in thickness, and should be soaked for 
an hour or more in water before being stretched upon 
the dialyzers. The membrane should be stretched as 
nearly uniform as possible upon the four dialyzers. 
Fit one dialyzer with parchment paper such as is fre- 
quently used for this purpose. Furnish one dialyzer 
with some other animal membrane e. g., a cow's blad- 
der or a rabbit's caecum. 

(2) Prepare dilute egg-albumin by adding to strained 
undiluted albumin about 9 volumes of distilled water. 

j. Experiments and Observations. 

(1) Salt, in saturated aqueous solution may be put 
into a dialyzer. So adjust the apparatus that the 
water in the outer receptacle shall be on a level 
with the solution in the vertical tube of the dialyzer. 
How much does the water rise in the tube ? What 
degree of positive pressure within the dialyzer does 
that represent? How much pressure per unit area, 
measured with a mercury manometer will it be nec- 
essary to produce within the dialyzer to stop the in- 
crease of the volume of its contents? (Endosmotic 
pressure.*) Will that amount of pressure prohibit 
diffusion between the liquids? 

(2) After osmosis has been allowed to take its unim- 
peded course for, say, one hour, starting with a 20 per 
cent, solution of NaCl within and distilled water with- 
out the dialyzer, note the height of the water in the 
tube and compute the number of grammes of water 
which have entered the dialyzer. Determine how 



DIGESTION AND ABSORPTION. 191 

much NaCl has passed out of the dialyzer. An easy 
and sufficiently accurate method is to evaporate to 
dryness all, or a known proportion of the liquid in 
the outer receptacle, and weigh the dry salt remain- 
ing. How many grammes of water enterthe dial- 
yzer for each gramme of salt that leaves ? (Endos- 
motic equivalent. ) 

(3) Is the endosmotic equivalent constant for salt and 
water? {a) Is it the same for different strengths 
of the salt solution, i. e., for 10% or 1% as for 20%? 
(£) Is it the same for two hours or four hours as 
for one hour ? 

(4) Fill with 10% glucose three dialyzers provided with 
three different kinds of membrane. Does osmosis 
take place at the same rate in all three dialyzers ? 
What is the endosmotic equivalent for glucose? 

(5) What is the endosmotic equivalent for dilute egg 
albumin? When albumin is injected into the colon 
it is readily absorbed as albumin, there being no 
digestive changes in it. 

(6) Fill a dialyzer with equal parts of 10% glucose 
and 10% NaCl. At the end of a convenient period, 
2-6 hours, determine whether these substances have 
diffused according to their own endosmotic equiva- 
lents, i. e., independent of each other, or have they 
been influenced the one by the other? 

(7) Fill a dialyzer with alcohol. Which way does the 
osmotic current flow? 

(8) In the above experiments water has uniformly 
passed into the dialyzer.* If pure water be taken 
into an empty stomach would one expect it to be 
readily absorbed ?f 

*If alcohol be taken into the stomach it is not diluted with water 
drawn from the tissue, but it is rapidly absorbed. 

fWater is absorbed slightly, if at all, through the walls of the 
stomach. 



F. VISION. 



XLIV. Dissection of the appendages of the eye. 

Appliances. — Fresh ox-eyes, including as much of the 
appendages as possible; physiological operating case; 
dissecting boards and pins, such as used for frogs; dog, 
cat or rabbit; bone forceps; injection mass; syringe. 

Dissection. -- Follow Gray; or Quain, Vol. III., Part III. 
(1) Before fixing the eye to the board make a careful 
examination of the organ. 

(a) Trace the conjunctiva, describing its ocular and its 
palpebral portions. Describe the plica semilunaris 
and the caruncula. Do these two tissues have the 
same relative size in man and the ox? Find and 
describe the puncta lachrymalia. Find and describe 
the openings of the lachrymal ducts. How many are 
there? Enumerate the conjunctival landmarks 
which determine the inner from the outer side of the 
eye. Enumerate the conjunctival landmarks which 
determine the superior aspect of the eye. Is the 
eye which you have a right or a left one ? 

(b) Observe the appendages of the eye. Do you find 
a remnant of the levator palpebral muscle ? Find 
the tarsal cartilages and the remnant of the orbicularis 
palpebrarium muscle. Find openings of the meibomian 

192 



VISION. 193 

and of sebaceous glands. Find and describe the 
lachrymal gland as to location and size. 

Find the cut-off ends of the recti and oblique mus- 
cles of the eye. 

Describe the location of the optic nerve with 
respect to the cornea. 

What traces have you found of the capsule of 
Tenon ? 

Enumerate the new landmarks which determine 
the superior aspect of the eye; the internal aspect. 
Are these extra landmarks sufficient to determine 
whether the eye which you have is a right or a 
left one? 

(2) Fix the eye to the board with corneal surface down, 
pinning down flaps of the conjunctiva for support. 

(a) Dissect out the four recti and the two oblique mus- 
cles. One will find in the ox a rather heavy retractor 
muscle in close relation to the optic nerve. This 
should be left undissected until the other muscles 
are demonstrated. 

(b) Trace further the intricate loculi of the capsule of 
Tenon. 

(V) Carefully separate from the eyeball all connective 
and adipose tissue. 

(3) Remove the retractor muscle of the ox eye in 
process of dissection, taking care not to sever any im- 
portant blood vessels or nerves. 

(a) Locate and describe the vencs vorticosce. How 
many are there? 

(b) Find the anterior ciliary arteries. How many can 
be found ? 

Describe their relation to the tendons of insertion 
of the recti muscles. What tissues do they supply? 

(c) Find the two long ciliary arteries. 



194 LABORATORY GUIDE IN PHYSIOLOGY. 

(d) Locate and enumerate the short posterior ciliary 

arteries. 
(<?) Dissect out the ciliary nerves. What tissue do 

they supply? 

(4) Let one number of the division dissect, for demon- 
stration, the orbital muscles of a dog, cat or rabbit. 
To facilitate the dissection fix the animal with dorsum 
up, and remove with bone forceps the upper and 
outer walls of the orbit. 

(5) Let one member of the division inject, with carmine 
or vermilion mass, the internal carotid of a dog, cat 
or rabbit, and dissect out for demonstration the ocular 
branches of the ophthalmic artery. 



XLV. Dissection of the eyeball. 

Appliances. — The eyes, already partly dissected, which 
have been kept in an ice chest; physiological operat- 
ing case. 

Dissection. — a. Anterior dissection: Fix the eye to the 
board, cornea upward, using the dissected muscles as 
guys. 

(1) Describe the cornea as seen from the front. Does 
the radius of curvature of the lateral meridian seem 
to be the same as the radius of curvature of the ver- 
tical meridian? With heavy scissors remove the cor- 
nea, leaving a margin of one-eighth inch anterior to 
its junction with the iris. 

Examine the cut surface of the cornea with a lens. 

(2) Through the elliptical opening thus made examine 
the iris as to texture, etc. 

(3) Holding the margin of the cornea with strong for- 
ceps, carefully dissect the sclerotic coat from the 
choroid for about one-eighth of an inch posterior to 
the angle of the anterior chamber. Locate four points 
in the margin from which incisions may be made 
antero-posteriorly between the insertions of the recti 
muscles. From the points located make the incisions 
posteriorly as far as the equator of the eyeball. Dis- 
sect each flap from the underlying choroid; remove 
the pins which fix the recti muscles, and through 
traction draw the flaps back; fix. 

{a) Make a drawing of the choroid with its irideal 
and ciliary portions thus exposed. 
195 



196 LAB OR A TOR V G UIDE IN PHYSIOL OGY. 

(b) Locate, if possible, the course and distribution of 
nerves and blood vessels. 

(4) With fine forceps grasp the margin of the iris and 
with fine scissors cut out a sector limited posteriorly 
by the ciliary body. 

(#) Study the boundaries of the posterior chamber. 

(b) Find fibers of the suspensory ligament. 

(c) Describe the anterior surface or the ciliary proc- 
esses. 

(5) Make a circular incision with small scissors severing 
the choroid and retina at about the line of the ora 
serrata. Lift off from the dense vitreous humor the 
whole ciliary apparatus and lens, place them, anterior 
surface downward, upon a plate. 

{a) Describe the posterior aspect of the ciliary proc- 
esses. 

(£) D ascribe the lens minutely, as viewed externally. 

(c) Make a section of the lens, describe its appearance. 
Is the capsule discernible ? 

(6) Describe the retina as seen through the vitreous 
humor. 

(a) Locate the entrance of the optic nerve. 

(b) Can the fovea centralis be located ? 

(c) Can the course of the retinal vessels be followed ? 
2. b. Posterior dissection. 

(V) Let one member of the division remove the poste- 
rior half of the sclerotic coat, after first fixing the eye 
with cornea downward, using the recti muscles, in 
this case also, for guys. 
{a) Note the vena vorticosce. 
(b) Follow the ciliary nerves from their entrance into 

the eyeball, along their course between the sclerotic 

and choroid coats. 



VISION. 197 

(V) Do you find the long ciliary arteries, or the poste- 
rior ciliary arteries ? 

(8) Remove the choroid carefully. 

(a) Note the character of its tissue, its vascularity 

and its rich pigmentation. 
(£) Describe the retina as seen from this direction. Its 

pigmented layer has probably come away with the 

choroid. 

(9) Remove the posterior half of the vitreous body 
together with the retina. 

(#) Make a drawing of the posterior surface of the lens, 
suspensory ligaments and ciliary processes as shown 
posteriorly. 

(10) Remove the remnant of the vitreous body; sever 
the fibers of the suspensory light; lift out the lens. 
(a) Describe the ciliary body and the iris thus held in 

their normal relations by the supporting sclera. 



XLVI. Physiological optics, a. Determination of indices 

of refraction of water and of glass, b. Determin= 

ation of focal distance of lenses, c. Verifi= 

cation of formula : ~ 4- A = ~ a d. A 

simple dioptric system. 

a. Determination of the indices of refraction of water 
and of glass. 

i. Appliances. — Apparatus for determining the index of re- 
fraction; a deep flat-bottomed water pan; a cube ot 
glass 4-6 cm. in linear dimensions and polished on at 
least two opposite sides. The two polished sides must 
be absolutely parallel, whether the other sides are par- 
allel makes no difference; centimeter rule and dividers. 

2. Preparation. — A very convenient and sufficiently exact 
apparatus for making the required determination may 
be readily made as follows: 

(1) Take a carpenter's tri-square, constructed wholly of 
iron; from the angle x (Fig. 26), where the gradu- 
ated limb joins the body, measure off centimeters upon 
the inner surface of the body and cut them in with a 
file. 

(2) Locate on the inner edge of the graduated limb any 
point, as y, 6 to 9 centimeters from the point x. 
With files remove about y 2 centimeter of the edge as 
indicated in the figure, cutting deeply at z, so as to 
leave a slender point at y as indicated. 

(3) Drill a hole in the inner surface of the body at o; 
fit and drive a heavy brass or iron wire into this; 
sharpen the upper end of the wire. The length of the 
wire above the body must be two or three centimeters 

198 



VISION. 199 

greater than the distance x y. Bend the point over so 

that the distance op shall equal x y. 
Experiments and Observations. — Place the instrument in 
the water pan; fill the pan, so adjusting it that both 
points p and y will just touch the water, or rather almost 
touch the water, for the surface of the water at y must 
be absolutely plane. If the point touch it the surface 
will not be plane. 




>s / a a a a a * a a~ 



L 



Fig. 26. 

Fig. 26. A contrivance for use in determining the refractive indices of 
water and of glass. 



(1) (a) Bring a small rule (r) into position and clamp 
it to the limb of the instrument by means of heavy 
serre-fine forceps. So adjust the rule that as one 
sights along its upper edge the points a, y and 3 seem 
to lie in one and the same straight line. Lift the ap- 



200 LABOR A TOR Y G UIDE IN PHYSIOL OGY. 

paratus out of the water and lay it upon the table, 

taking care not to disturb the adjustment. 

(b) With dividers measure the distance from the point 
y to line 3. This is the radius. Determine the point 
where the circumference would cut the upper surface 
of the rule, say point b. 

(V) From this point determine the perpendicular dis- 
tance to the edge of the limb at c. 

(d) The line c y x is a normal to the surface of the water 
at the point y. The angle i is the angle of incidence; 
the angle r is the angle of refraction. Imagine a circle 
whose center is at y and whose circumference passes 
through b and 3. The line b c is the sine of the angle 
of incidence. The line x 3 is the sine of the angle 
of refraction. 

(e) What is the ratio of sin i to sin r, or ^-^ = ? 

v J ' sin r 

(2) In the same manner determine the ratio of the sines 
of these angles when the rule is so adjusted as to 
bring a'y 6 in apparently one straight line. What is 

the ratio of sin i ' to sin r ' ? or 5£i! — ? 

sin r 

(3) If the instrument has been carefully constructed 
and if the determination has been made with suffi- 
cient care, the ratios will be found to be practically 
equal, i. e., ^ = §^ • What is the constant ratio in 
the case of water? This constant ratio is called the 
index of refraction, and is conventionally represented 
by fi. 

For water, *= £-J = f= 1-888. 

(4) To determine the index of refraction of glass pro- 
ceed as in the case of water. Set the instrument upon 
the table; the block of glass may be placed upon the 
body of the instrument, the polished surfaces be- 
ing placed above and below. If the distance be- 



VISION. 201 

tween the polished surfaces is not equal to x y, a point 

y' may be located on the upper surface near the edge 

of the glass block by making a dot with ink where the 

line y x cuts the upper surface of the block. This line 

is the normal. 

What is the index of refraction of the glass block 

furnished by the demonstrator? 

b. The determination of the focal distance of lenses. 

By means of a spherometer the radius of curvature (r) 

of a lens may be determined.* 

If one knows the radius of curvature of a lens and the 

index of refraction of the material of which the lens is 

made he may compute the focal distance by using the 

r r 

formula (1) Y-— for piano convex lenses, or (2) F=^7— t 

for bi-convex lenses. But there is an easier and more 

direct method of determining the focal distance of a lens; 

namely, by direct experiment. 

/. Appliances.— An instrument such as is used in physical 
laboratories for the same purpose or such a one as is 
described under 2; several lenses ranging from 5 cm. to 
50 cm. in focal distance. 

2. Preparation. — A most satisfactory apparatus for this 
purpose may be made by any student or demonstrator in 
three or four hours. From thin pine boards construct a 
simple box about 10 cm. square in cross section by 50 
cm. in length. One end of the box should be closed 
with a tightly stretched oiled paper for a screen, while 
the other end may be closed with the same material of 
which the rest of the box consists, the center of the end 
having a circular aperture one or two centimeters in 

12 a, 
*[r= — \— , when a=spherometer reading, and l=the length of 

one side of the equilateral triangle determined by the legs of the 

spherometer.] 



202 



LAB OR A TOR Y G UIDE IN PH YSIOL OGY. 



diameter. The bottom of the box is constructed as fol- 
lows: (See Fig. 2*7.) Cut through the middle of the bot 
torn a slot about 0.5 cm. wide and 45 cm. long. Make a 
lens carrier of wood as indicated in the figure (Fig. 27, 
C. & C'.). The saw groove in the top of the carrier 
serves to hold the lens. If, however, the lenses to be 
used in the apparatus be not provided with rims and 







Fig. 27. 



Fig. 27. Showing parts of apparatus for determining the focal distance 
of lenses. For construction of the apparatus, see XLVI=b=2. 

rings the demonstrator can readily contrive a means of 
holding them in place. In any case they should be so 
held that the plane of the lens is perpendicular to the 
axis of the box, and that the center of the lens (o) 
is virtually over a fixed line (o') drawn transverse to the 



VISION. 203 

axis of the lens carrier. The screws S and S' serve the 
double purpose of protecting the projection (p) from 
splitting off and of affording handles by which the car- 
rier may be slipped along the groove. Along one edge 
of the groove on the outer surface of the bottom make a 
centimeter scale carefully with a sharp hard lead pencil. 
The s*cale should have its zero point in the plane of the 
screen. At the point D fix a shaft (such a one as shown in 
Fig. 21-, D'), which shall extend several centimeters below 
the bottom and set perpendicular to it. The shaft may 
be fixed in a universal clamp-holder and the whole sup- 
ported upon a heavy support. By adjusting the clamp- 
holder the apparatus may be directed toward any desired 
object. Make a cover to the box, and blacken the whole 
inside. 

3. Observations. — Fix a lens in place; c4ose the box; direct 
its axis toward some well illuminated distant object; 
grasp the handles of the lens carrier and move it to a 
position which gives upon the screen a sharply defined 
image of the object in the field. One has only to read 
the position of the transverse line of the carrier on the 
centimeter scale to have the focal distance of the lens; 
i. e., the distance at which parallel rays are focused. 

c. Verification of the formula \ + \r — ^. 

i ' v F 

A second method of determining the focal distance of a 
lens depends upon the relation of the distances of the conju- 
gate foci to the general focal distance: This relation maybe 
expressed thus: The sum of the reciprocals of the conjugate 
foci is equal to the reciprocal of the focal distance. ^— h|^— p* 
Now when a lens throws upon a screen the image of an 
object it is evident that the distance of the object (o) 
represents one and the distance of the image (i) represents 
the other of these conjugate focal distances; so one may 



204 



LABORATORY GUIDE IN PHYSIOLOGY. 



say: The reciprocal of the distance of the object from the lefts 
( — ) plus the reciprocal of the distance of the image (y) 
e quals the reciprocal of the general focal distance ^ : thus 
(— -}-i-. = ^ ). This formula enables one to compute 
the focal distance after first determining by experiment the 
values o and i. Inasmuch as the student has already deter- 
mined the focal distance (F) and may not have made the 
rather extended computation incident to the derivation of 
the above most valuable formula it is considered that the 
most profitable course to pursue at this point is the verifi- 
cation of the formula. 



fi 



'/•"■'"7""'"T" , '" ,, /""£T 



r '""l"" l" ,n i 



"■T""-t 



§ 




Fig. 28. 

Fig. 28. An apparatus for determining the conjugate focal distance 
For description, see C=l. 

/. Apparatus. — To that end one may construct a simple 
apparatus (Fig. 28). For the determination of the focal 
distance it is usual to have both object and lens mova- 
ble. For our purpose this may be dispensed with as it 
lends little to the reliability of the result and detracts 
much from the simplicity of the apparatus. Upon a 
thin board as a base fix an upright piece near one end 
of the base, whose inner surface may be painted white 
and serve as a screen (S). Near the other end fix a 



VISION. 205 

second upright piece having in its center a large hole. 
Over this hole, on the inner surface of the upright, fix a 
sheet of lead or of copper in which some figure has been 
cut (o). Construct a lens carrier (c), whose pointer (p) 
will indicate upon the scale (s') the position of the center 
of the lens. The use of the instrument will be some- 
what facilitated if the distance between the surface of 
the screen and the surface of the lead or copper be pur- 
posely made exactly 100 cm. In addition to the above 
apparatus one needs the lenses whose focal distance he 
has determined. He needs also a lamp or candle to 
place behind the metallic screen at e. 
Experiments and Observations. — Place a light behind the 
metallic screen; it shines through the figure cut through 
the screen. This figure is the object. 

(1) (a) Place a lens in the carrier and so adjust it that 
the plane which it represents is perpendicular to the 
axis of the instrument and its center is in the same 
perpendicular plane with the index (p) of the carrier. 

(b) Slide the carrier along the base until the object is 
sharply focused upon the screen. 

(c) Read from the scale the distance of the lens from 
the image (i). If the instrument is made just 100 cm. 
between screen and object, then the difference be- 
tween 100 and the reading will be the distance of the 
lens from the object. Is the image erect or inverted? 
Explain the phenomenon, drawing geometric figure. 

(2) Study the general formula: 

(«) i+\='r 

(b) F=^; but 0+1 = 100; therefore 
(V) 100 F = o i. 
From this form of the statement it is evident that the 



206 LABOR A TOR Y G UIDE IN PHYSIO LOG Y. 

lens will throw a distinct image in either one of two 
positions. Demonstrate it experimentally. 
(3) Determine o and i for each lens and substituting 
their values and that of F previously determined, 
verify the equation. A moderate deviation may be 
expected, due to errors in the apparatus and in the 
observations, 
(j) Problems. 

The value of the formula — -|— r = ^ is so great and 
its application so frequent that the student should 
thoroughly familiarize himself with the properties 
of lenses as revealed in this formula. 
Solve the following problems: 

(1) When the object is twice the focal distance, 
what is the distance of the image ? 

(2) When the distance of the object is greater 
than 2F, how does the distance of the image com- 
pare with 2F ? 

(3) When the object is at a very great distance 
(o= co) at what distance will the image be formed? 

(4) What is the maximum focal distance that 
may be determined or verified with the above de- 
scribed apparatus ? Discuss methodically. 

d. A simple dioptric system. 

The simplest dioptric system is one in which the ray 
passes from one medium into a second medium of 
different refractive index, the surface of separation 
of the two media being a spherical surface. In the 
accompanying figure (Fig. 29 A) the spherical sur- 
face s'sps" separates the medium M, whose re- 
fractive index is 1.000, from the medium M', whose 
refractive index is 1.500. 

Note the following cardinal points of a simple 
dioptric system. 



VISION. 



207 



The center of curvature of the spherical surface 
(n) in the nodal point. 

That radius which is the center of symmetry of 
the dioptric system (e. g., n — p.) is called the princi- 
pal axis of the system. In this axis lie the first and 
second principal foci, f and f respectively. The point 
where the optical axis cuts the spherical surface 
(p) is called the principal point. The plane tangent 
to the spherical surface at this point is the principal 





m 


dy'^ 


^i- c 


m 








^— -^^ ,.-' 




i 


"^-. 














J£? 




~~~~ — 4^ 


\ 






r' 






?i^- 


n -— 




^ 


J 


J 


~~~— ~\<s* 




?^^ 








\ 


A 










Fig. 29. 

Fig. 29. A. Showing the cardinal points of a simple dioptric sys- 
tem, n, nodal point; R p n, principal axis; p, principal point; f, £', 
principal foci. 

Fig. 29. B. Showing the relation of the visual angle, v and the 
size of object and image to values p and n. 

plane. Planes perpendicular to the optical axis at 
f and f are called the first and second principal focal 
planes respectively. 

Problem. Given the radius of curvature and the 
index of refraction to locate upon the principal axis 
the principal foci. 

Neumann has given the following construction: 



208 LABOR A TOR Y G UIDE IN PHYSIOL OGY. 

(1) Erect at n and p perpendiculars to the principal 
axis. 

(2) Lay off, upon each, the two indices of refrac- 
tion of the two media, measured from the origin 
of each perpendicular, in the same linear units 
used in measuring the radius. In the figure let 
n c and p d represent the index of refraction of 
the medium M, and n a and p b the index of re- 
fraction of medium M\ The continuation of line 
a d cuts the principal axis in the point f, the first 
principal focus, while the line b c cuts it in the 
point P, the second principal focus. The geo- 
metrical figure shows the following important 
properties of the dioptric system: 

I. The distance from the first principal focus to 
the principal point equals the distance from the 
second principal focus to the nodal point. 

(1) Mathematically expressed: pf=nP. 

II. The ratio of the second focal distance (pP) to 
the first (pf) is equal to the ratio of the index 
of refraction of the second medium (M') to that 
of the first (M).* 

(2) Mathematically expressed: — pf: pP = /j>: pS. 
But pf = nP; substitute this value in the second 
equation, — 

(3) .... nP: p£'=/i: /±'; assume medium M to have 
an index of refraction fi=l, 

(4) nP:pP=l:/A 

(5) pP = nf'xy; or more concisely 

(5') p — /y/n. (See p and n in Fig. 29. A.) 
This derived property of the construction merits 
a separate formulation. 
*Refraction and Accommodation of the Eye. — Landolt, p. 85. 



VISION. 209 

III. The distance from the second principal focus 
to the principal point equals the product of the 
distance from that focus to nodal point multi- 
plied by the index of refraction of the second 
medium (p=#'n). 

Note in addition the following facts regarding 
the effect of such a dioptric system upon light. 

1st. The ray rs, meeting the spherical surface 
perpendicularly, will not be refracted at s, but 
will pass on through the nodal point. 

2d. The ray r's', parallel to the principal axis in 
the first medium is refracted at the spherical sur- 
face and cuts the principal axis at P, — it passes 
through the second principal focus. 

3d. The ray r"s", cutting the principal axis at f 
in the first medium (M), is refracted at s" and 
traverses the second medium parallel to the prin- 
cipal axis. 



XLVII. Physiological optics, applied, a. The application 

of the laws of refraction to the mammalian eye. 

b. To locate in the mammalian eye 

the cardinal points of the sim= 

pie dioptric system. 

The dissection of the ox eye revealed several refractive 
media (cornea, aqueous humor, lens, and vitreous humor) 
and several curved surfaces bounding these media. In 
determining the focal distance of a lens one must know the 
radius of curvature and the refractive index. In determin- 
ing the focal distance of a system of refractive media and 
surfaces one must know (1) the radius of curvature of each 
surface, (2) the refractive index of each medium, and (3) 
the location of their cardinal points upon the principal 
axis of the system. 

The mammalian eye receives its light through media 
and surfaces, as indicated in the following table: 



MEDIA. 


INDEX OF 
REFRACTION. 


SURFACE. 


RADIUS 


Air. 
Tear Film. 


1.000 
1.3365 






Over Ant. Surf. Cornea. 


7.8'29+ cm. 


Cornea. 


13367 


• Ant. Corneal Surface. 


7.829+ cm. 


Aq Humor. 


13365 


Post. Corneal Surface 


7.829— cm. 


Lens. 


1 4371 


Ant. Surface. 


10.0 cm. 


Vit. Humor. 


1.3365 


Post. Surface. 


6.0 cm. 



This array of media and surfaces would seem to make 
a problem too intricate to solve with the means at our dis- 
posal. Notice, first that the tear film and the ant. and 
post, corneal surfaces have the same radius of curvature; 

210 



VISION. 211 

i.e., though curved surfaces they are parallel and form a 
case under the following theorem: "If a ray pass from 
any medium through a denser medium which is bounded 
by two parallel planes it emerges from the denser medium 
in a line parallel to its course before entering that 
medium." It is customary at this point to take the ante- 
rior surface of the cornea as the first refractive surface 
and ^=1.3305. 

Notice that the index of refraction of the aqueous humor 
and vitreous humor are the same. It is now evident that 
we have to deal with three media [air, aqueous or vitreous 
humor, and lens], with three surfaces [ant. corneal surface, 
ant. and post, lens surface], whose radii are 7.829, 6 and 
10 respectively. But even this great step toward simpli- 
fying the problem leaves us with a long road before us un- 
less we can find a short cut. " It has been shown mathe- 
matically that a complex optical system consisting of sev- 
eral surfaces and media, centered on a common optical axis, 
may be treated as if it consisted of two surfaces only." 
[Text-book of Physiology— Foster, 1891— vol. IV., pg. 9.] 
The location of these surfaces and the cardinal points are 
given as follows by Landolt : 

A. The normal eye. 

The point r (Fig. 30.) where the principal axis cuts the 
cornea is 22.8237 mm. from the second principal focus f 
(the retina) ; c, the center of curvature of the cornea; s, the 
point where the optical axis cuts the anterior surface of 
the lens, is 3.6 mm. from r, the point where the optical 
axis cuts the posterior surface of the lens 7.2 mm. from 
r; 1, the center of curvature of ant. surface of lens; 1', 
the center of curvature of posterior surface of lens. 

B. The accurate mathematical reduction. 

The reduction referred to in the text above is represented 
by the two refractive surfaces with nodal points n and n' 



212 



LABORATORY GUIDE IN PHYSIOLOGY. 



radii of 5.215 mm. each and cutting the optical axis at p 
and p', located 1.7532 mm. and 2.11 mm. respectively 
from r. 
C. The final approximate reduction. 

Note that p is less than 0.36 mm. from p'. One may as- 
sume one nodal point N, and one refracting surface between 
the computed ones, cutting the principal axis at P, and 
introduce an error too slight to consider. But this brings 




g ? f 



^p/aidCr,^ 



J 



Fig. 30. 

Fig. 30. Showing the mathematical features of the reduced eye. 
For detailed explanation of the figure see text A, B and C. The figure 
is multiplied by five in its linear dimensions. [Errata : For 6 cm read 
3 cm] 

us back to the simplest possible dioptric system, already 
described on pg. 206 et. seq. 

All of the properties of that simple dioptric system 
are possessed by the normal mammalian eye. 
b. To locate, experimentally in the mammalian eye, the 

cardinal points of the simple dioptric system. 
i. Appliances and Materials. — A white rabbit; support with 
universal clamp-holder and small cork-lined burette 



VISION. . 213 

clamps; meter stick or tape; steel or ivory rule, with 
millimeters subdivided if possible, hand lens, fine divid- 
ers with needle points; bone forceps; NaClO.6%; camel's 
hair pencil; absorbent cotton. 
2. Preparatio7i. — (1) Mathematical, (See Fig. 29 B.) 
We wish first to locate the nodal point in a rabbit's eye. 
Represent the distance from the retina to the nodal 
point by n, the distance from the object to the image by 
d, the vertical dimension of the object by o, the same 
dimension of the image by i. From the similar right 
triangles of the figure one may write: 

(1) o: i = d — n: n; 

(2) on = id — in; 

CO » =& 
Jnder the conditions of the experiment i is so small 
compared with o that it may be ignored in the denomi- 
nator, and we may use the equation: 

(*) n =" 

(2) Arrangement of Apparatus. 

{a) A convenient object to observe is a well-illumi- 
nated window, or one sash of a window; measure 
the vertical distance between the horizontal strips 
of the sash. 
(b) Arrange three or four tables end to end in a line 
perpendicular to the plane of a window. On the 
table lay off from the plane of the window the dis- 
tances 4, 4.5, 5, 5.5 and 6 meters. 
j. Operation. 

(1) Remove an eye from the rabbit which had been 
chloroformed some time before and suspended by the 
anterior limbs. 

(2) Dissect from the eye, especially from the posterior 



214 LABORATORY GUIDE IN PHYSIOLOGY. 

aspect of it, all of the areolar connective tissue, muscle 
tissue, etc., down to the glistening smooth sclera. 

(3) Wrap around its equator a band of absorbent cot- 
ton wet with normal solution. 

(4) Fix the eye in the clamp with its axis transverse to 
the axis of the clamp, tpking care to exert just enough 
pressure to prevent the eye from falling on being 
touched, but not enough to distort it. 

(5) Fix to the clamp a thread with a bit of lead to serve 
as a plumb line. 

^. Observations. 

(1) Adjust the support so that the eye is directed toward 
the object and the image is located approximately 
symmetrically about the fovea centralis, and the plumb 
line over the mark 4 meters. With the fine dividers 
measure in the image the distance between those 
points which were chosen as the limits of the object. 
The value of this measurement may be read to tenths 
of millimeters by laying the divider points upon the 
steel rule and reading with the hand lens. 

(2) Make similar observations at 4.5 m., 5 m., 5.5 m., 
and 6 m. Each observation should be made three or 
four times and the average taken. 

(b) Record these averages in a table ruled with columns 
for the values d, o, i, n and p. 

(4) Calculate for column n the values obtained by sub- 
stituting, in the formula n=^, the values observed in 
(1) and (2). What is the value of n ? 

(5) Measure the antero-posterior diameter of the eye. 
How far anterior to the posterior surface of the sclera 
is n located? How far from the surface of the cornea? 
How does the ratio of these two quantities differ from 
that given above for the human eye? 

(6) Locate the position of the principal point or the 



VISION. 215 

point where the ideal refracting surface of the eye 
cuts the optical axis, by applying the formula: 

Assuming for ;x the value which it has been calculated 
to have in the human eye (1.3365 Landolt, p. 86), 
how far is this point posterior to the anterior surface 
of the cornea ? How does your result compare with 
that for the " reduced human eye? " 

(7) Is the image erect or inverted? Explain the phe- 
nomenon ? 

(8) Move the eye to within one meter of the object. 
Note that a fairly clear image may be thrown upon a 
posterior segment of the sphere, which is many hun- 
dred times the area of the fovea centralis. 

(9) If a fine sharp needle be thrust through the eyeball, 
following a course perpendicular to the optical axis 
and cutting it at n, what relation would this needle 
have with the lens? Would it be tangent to the lens; 
would it enter the lens or would it pass free of its pos- 
terior surface? 

(10) If a similar experiment were performed with refer- 
ence to the point p, what relation would the needle 
have to the anterior surface of the lens ? 

For these experiments the eye may be frozen after 
the introduction of the needle and a vertical longi- 
tudinal section made. 



XLVIII. Accommodation and convergence. 

In the above experiment with the excised rabbit's eye 
one notices a marked blurring of the image when the eye 
is brought near the object. Though the definition of the 
image is sharp at 5-6 meters or beyond, at 2 or 3 meters 
the outlines are hazy. The normal living eye is, however, 
able to give one the sensation of a clear image at any distance 
from several inches to several miles. That there is actually 
a sharply defined image upon the retina when the normal 
mind has the sensation of such an image there is no doubt. 
One knows from his experience with optical instruments 
that they must be readjusted for each distance if they are 
to yield a sharp image for each distance. 

The same thing is true in the case of the organic optical 
instruments with which one perceives the form, color and 
space relations of the objects of his environment. The 
functional adaptation of the visual organs to distance is called 
accommodation. 
a. Accommodation. 
Experiments and Observations. 

(1) Take a sharp pointed pencil or similar object in each 
hand; hold the upturned points in the line of direct 
vision before the eye, one point being about 25 centi- 
meters distant from the eye and the other at arm's 
length; make the observations with one eye, the other 
being closed or screened. 
(a) Focus upon the near point. Is the image of the 

distant point clear? 
(£) Focus upon the distant point. Is the image of 
the near point clear? 

216 



VISION. 217 

(V) While the eye is focused steadily upon the near 
point bring the distant point slowly up to a position 
beside the near point. One of the images is trans- 
formed from an ill defined one to a clearly denned 
one. Which image is it ? Does one note a similar 
change in the definition of the image when he 
moves the near point out to position beside the dis- 
tant point while focusing steadily at the latter? 

(d) Sum up the results of the experiment into a con- 
cisely formulated statement. 
(2) Holding the two points side by side at a distance of 

30 centimeters note that the points appear equally 

well defined. 

{a) Direct the eye steadily at one of the points while 
moving the other one nearer to the eye. Note the 
number of centimeters which it advances toward the 
eye before the outlines become ill-defined. Reverse 
the act, moving the point back to its original posi- 
tion beside the stationary point, noting that the 
image of the receding point remains clear. 

(b) Continue to carry it farther from the eye, noting 
that after it has been carried beyond the unmoved 
focused point a certain distance the outline be- 
comes again ill-defined. Note the number of centi- 
meters between the two points in this position. 

(<r) Make a similar experiment, using 50 cm. for 
the distance of the stationary point, and note the 
centimeters between the points at the limits of 
clear definition. In this way one may observe and 
measure the depth of focus of the eye. 

(//) Is the depth of focus greater at 30 cm. or at 
50 cm. ? 

(<?) Is the depth of focus greater at 100 meters than at 
one meter ? Demonstrate and explain. 



218 LABORATORY GUIDE IN PHYSIOLOGY. 

(3) Determination of the near point or "punctum prox- 
imum." Determine the distance from the eye of the 
nearest point at which a pencil point or needle may 
be perfectly clearly seen. The exact location of the 
near point may be more satisfactorily determined if 
one look at the object through two holes, 2 mm. apart, 
in a card. At this point thepunctum proximum act 
of accommodation is brought most actively into play. 

(4) Determination of the punctum remotum. 

(a) Direct the eye toward some object not less than 
six meters away and describe to other members of 
the division the minute details of the object, such as 
slight irregularities of surface lines or other details. 
If an individual is able to convince his comrades that 
he can perceive, at this distance the minute details 
of objects he must be credited with normal vision. 
Inasmuch as he can also see with the usual distinc- 
tions more distant objects the punctum remotum is 
said to be located at infinity; or, to state it in another 
way, the eye is able, with suspended accommodation, 
to bring parallel rays to a focus upon the retina.* 

(o) It frequently happens that the individual under 
observation fails to make out more than the merest 
outline of an object 6 meters away. Decrease the 
distance until he is able to perceive details seen by 
the majority of his comrades. If this distance has 
to be decreased to two or three meters the determi- 
nation may be made more exact by resorting again 
to the needle and punctured card mentioned in (a), 
and carrying the needle away until it appears double. 

*It must be stated here that this experiment does not make it cer- 
tain that the punctum remotum is not beyond infinity! In a subsequent 
les>on that point will be carried farther. We must be temporarily con- 
tent with having it so far. 



VISION. 219 

In recording the punctum remotum, write infinity (oo ) 
for six meters or more and for any distance within 
that, record in meters and decimals thereof. 

(5) How many meters from the punctum remotum to the 
punctum proximum in those cases where the punctum 
remotum is less than six meters ? 

(6) Observe the pupil closely while the subject directs 
the eye from a distant object to a near one. It con- 
tracts slightly. On a priori grounds this act of the 
iris is advantageous. Showfrom the standpoint of the- 
oretical optics why it is advantageous. 

(7) Observe from the side that when the act of accom- 
modation takes place the iris at the edge of the pupil 
not only moves toward the center but advances notice- 
ably toward the cornea. What could produce this? 
{a) If the edge of the iris rests upon the lens capsule 

would it not be pushed farther toward the cornea 
incident to its contraction toward the center? 

If the pupil contracted from a 3 mm. diameter to 
a 2 mm. diameter, how much would it be advanced 
incident to the normal curvature of the lens. Could 
this be detected by the method of observation which 
has been employed ? 
(£) Account for the forward movement of the pupillary 
edge of the iris during accommodation. 
b. Adaptation of the eye for direction. Convergence. 

Just as the eye possesses a mechanism by which it 
changes its refractive power for different distances, so it 
possesses a mechanism by which it may change the direc- 
tion of its visual axis from one object to another or may 
follow the movements of objects within the range of vision. 
I. Monocular fixation. — Let two individuals work together, 
one as subject and the other as observer. Let them sit 



220 LABORATORY GUIDE IN PHYSIOLOGY. 

on opposite sides of the table. Let the subject close or 
screen one eye. 

(1) Hold any object directly in front of the subject; let 
the subject keep his gaze continually fixed upon the 
object. Move the object quickly toward the subject's 
left, and note the fixation anew of the object in its new 
position. What muscle or muscles accomplished this 
act of monocular fixation? 

(2) Move the object quickly in the opposite direction, 
then upward, downward and diagonally, noting the 
instantaneous adaption of the eye to the new 
direction, recording also the muscle or muscles involved 
in each act. Are all the movements apparently equally 
ready and exact ? 

(3) Bringing the object to a point directly in front, 1 m. 
distant, note through how great a lateral movement it 
may be carried without inducing any discernible change 
in the visual axis of the eye. 

(4) Bring the object to the central position and move it 
very slowly outward in any direction, noting whether 
the changes in the direction of the visual axis are 
equally slow and regular. 

2. Binocular fixation, convergence. 

In the above experiments it was probably noted by both 
subject and observer that the closed or screened eye 
responded to every movement of the other eye. 

(5) With both eyes open and fixed upon an object held 
directly in front at a distance of about 1 m., let the 
observer move the object quickly, then slowly, right, 
left, up, down, and around, and observe the continuous 
perfect fixation of the object with both eyes. 

(a) What muscles are involved in following an object 
from one's right side to his left ? In each other di- 
rection in turn? 



VISION. 221 

{3) Do all of these muscles seem to act perfectly in 

all of the subjects examined ? If not; describe any 

variation. 
(0) Convergence, (a) Let the subject direct his gaze at 
the tip of the observer's ear, and without warning 
change his point of binocular fixation to some distant 
object in the same line of vision. What change in 
the eyes of the subject is noticeable by the observer? 
What muscles were involved in producing the change ? 
(£) Hold an object in front of the subject and 1 m. 

distant. Move it directly toward the subject's eyes 

and note the convergence of the lines of vision of 

the two eyes. What muscles perform the act ? 
(V) Through how short a distance may the object be 

moved in the direct line of vision without causing a 

discernible change of the angle of convergence of 

the two eyes. 
(d) From the central, 1 m. position, carry the object 

to a point about }4 m. to the right, and j4 m. 

above the eyes of the subject. What muscles are 

involved in the act of convergence ? 
(<?) Is the power of convergence apparently normal in 

all members of the class ? If not, describe minutely 

any variations. 



XLIX. Miscellaneous experiments.* 

a. Schei?ier' 1 s experi?nent. 

(1) Prick two smooth holes in a card at a distance from 
each other less than the diameter of the pupil. Fix 
two long, fine needles or straws in two pieces of wood 
or cork. Fix the cardboard in a piece of wood with a 
groove made in it with a fine saw, and see that the 
holes are horizontal. Place the needles in line with 
the holes, the one about eight inches, the other about 
eighteen inches from the card. 

(2) Close one eye, and with the other look through the 
holes at the near needle, which will be seen distinctly, 
while the far needle will be double, both images 
being somewhat dim. 

(3) With another card, while accommodating for the 
near needle, close the right-hand hole, the right-hand 
image disappears; and if the left hand hole be closed, 
the left-hand image disappears. 

(4) Accommodate for the far needle, the near needle 
appears double. Now close the right-hand hole, and 
the left hand image disappears; and on closing the 
left-hand hole, the right-hand image disappears. 
[Practical Physiology — Stirling.] 

(5) Explain the phenomena, drawing figures which show 
just what must take place in the eye. 

*The miscellaneous experiments of Lesson XLIX have been taken 
from Stirling's Practical Physiology. The author takes this place and 
opportunity to acknowledge his indebtedness to Prof. Stirling. 

222 



VISION. 223 

(d) Pur kinje- Sanson's images. 

(6) In a dark room, light a candle and hold it to one 
side of the observed eye and on a level with it. Ask 
the person to accommodate for a distant object, and 
look into his eye from the side opposite to the candle, 
and three reflected images will be seen. At the 
margin of the pupil, and superficially, one sees a small 
bright erect image of the candle flame reflected from 
the anterior surface of the cornea. In the middle of 
the pupil there is a second less brilliant and not 
sharply defined erect image, which, of all the three 
images, appears to lie most posteriorly. It is reflected 
from the anterior surface of the lens. The third image 
lies toward the opposite margin of the pupil, is the 
smallest of the three, and is a sharp inverted image, 
from the posterior surface of the lens. Ask the person 
to accommodate for a near object, and observe that 
the pupil contracts, and the middle image — that from 
the anterior surface of the lens — becomes smaller and 
comes nearer to the corneal image. This shows that 
the anterior surface of the lens undergoes a change in 
its curvature during accommodation. 

(7) Place in a convenient position on a table a large 
convex lens, supported on a stand. Standing in front 
of it, hold a watch glass in the left hand in front of 
the lens and a few inches from it. Move a lighted 
candle at the side of this arrangement, and observe 
the three images described above. Substitute a con- 
vex lens of shorter focus, and observe how the images 
reflected from the lens become smaller. [Practical 
Physiology — Stirling.] 

(8) Explain the phenomena, using drawings. 
c. The blind spot. 

(9) Marriotte's experiment. — On a white card make a black 



224 LABOR A TOR Y G UIDE IN PHYSIO LOG Y. 

cross and a circle about three inches apart. Closing 
the left eye hold the card vertically about ten inches 
from the right eye and so as to bring the cross to the 
right side of the circle. Look steadilyat the cross with 
the right eye, when both the cross and the circle will 
be seen. Gradually bring the card toward the eye, 
keeping the axis of vision fixed on the cross. At 
a certain distance the circle will disappear, i. e., when 
its image falls on the entrance of the optic nerve. On 
bringing the card nearer, the circle reappears, the 
cross of course being visible all the time. 

(10) Map out the blind spot. 

Make a cross on the center of a sheet of white paper 
and place it on a table about ten or twelve inches from 
you. Close the left eye and look steadily at the cross 
with the right eye. Wrap a penholder in white paper, 
leaving only the tip of the pen point projecting, dip 
the latter in ink, or dip the point of a white feather in 
ink, and keeping the head steady and the axis of vision 
fixed, place the pen point near the cross and gradu- 
ally move it' to the right until the black becomes in- 
visible. Mark this spot. Carry the blackened point 
still further outward until it becomes visible again. 
Mark this outer limit. These two points give the 
outer and inner limits of the blind spot. Begin again 
moving the pencil first in an upward and then in a 
downward direction, in each case marking where the 
pencil becomes invisible. If this be done in several 
diameters an outline of the blind spot is obtained, 
even little prominences showing the retinal vessels 
being indicated. 

(11) To calculate the size of the blind spot. 
Helmholtz gives the following formula for this purpose: 
When / is the distance of the eye from the paper, F 



VISION. 225 

the distance of the second nodal point from the retina — 
usually 15 mm. — d the diameter of the sketch of the 
blind spot drawn on the paper, and D the correspond- 
ing size of the blind spot: -|=|orD = F !?. 
The macula hctea or yellow spot. Maxwell's experiment, 

(12) Make a strong solution of chrome alum — filter it, 
and place it in a clear glass bottle with flat sides.. 
Close the eyes for a minute or so, open them, and 
while holding the chrome alum solution between one 
eye and a white cloud, look through the solution. An 
oval or round rose spot will be seen in the otherwise 
green field of vision. The pigment in the yellow spot 
absorbs the blue-green rays, hence the remaining 
rays which pass through the chrome alum give a rose 
color. 

(13) Is it possible to calculate the size of the macula 
lutea ? 

Shadows of the fovea centralis and retinal blood vessels. 

Move, with a circular motion, a blackened card with 
a pinhole in its center, in front of one eye looking 
through the pinhole at a white cloud. Soon a punc- 
tated field appears with the outlines of the capillaries 
of the retina. The oval shape of the yellow spot is 
also seen, and it will be noticed that the blood vessels 
do not enter the fovea centralis. Move the card ver- 
tically, when the horizontal vessels are most distinct. 
On moving it horizontally, the vertical ones are most 
distinct. Some observers recommend that a slip of 
blue glass be held behind the hole in the opaque card, 
but this is unnecessary. 



L. Perimetry. 

In the foregoing experiments we have dealt exclusively 
with what is called direct vision, i. e., with phenomena in- 
volving the formation of a clearly denned image upon the 
macula lutea. Every one has noticed that outside the range 
of direct vision one may still get a pretty definite idea not 
only of form but of color as well. It is the purpose here 
to ascertain just how far this field of indirect vision extends 
in every direction from the visual axis; or, to locate the peri 
meter of the field of indirect vision. Various instruments 
have been devised — called perimeters to aid one in peri- 
metry. 

All of these appliances have for their object the map- 
ping of the field. In all exact methods the map takes the 
form of a polar map, the pole corresponding to the point 
where the line of vision would pierce perpendicularly the 
plane of the map. 
i. Appliances. — A perimeter, or ruled blackboard, Fig. 32; 

perimeter charts, such as shown in Fig. 33. 
2. Preparation. — A very economical and exact perimeter 
may be constructed in the following manner : 

Take a blackboard whose dimensions are abont 1 m. by 
1.5 m. Locate a point 40 cm. from one end and 50 cm. from 
either side. Let this be the point of fixation or the 
point where the line of direct vision falls upon the sur- 
face of the board. 

We propose now to draw upon the board a series of 
circles whose distance from one another shall represent 
an angular distance of 10°. Reference to Fig. 31 makes 

226 



VISION. 



227 



it evident that if the line A B represent the plane sur- 
face of the blackboard and if the eye be placed at O the 
equal increments of 10° on the quadrant become a series 
of increasing increments upon the surface of the 
board. The numbers at the right (Fig. 31) show just 
how many centimeters the radius of each successive 
circle should be provided the distance of the eye from 
the board be taken at 20 centimeters. 




Fig. 31. 

Fig. 81. For de- 
scription see 
L=2. 



Fig. 32. Showing method of ruling a black- 
board for use in perimetry. The radii of the cir- 
cles are given at the line A B in Fig. 31. 



After drawing the circles, draw meridians which divide 
each quadrant into three to nine subdivisions. The 
completed blackboard chart will have the appearance 
and proportions shown in Fig. 32. The circles and 



228 LABORATORY GUIDE IN PHYSIOLOGY. 

meridians should be traced permanently in slate-colored 
enamel upon the surface of the blackboard. Any marks 
made upon the board with chalk may then be erased 
without disturbing the perimeter circles. 

Make test objects in this manner. To a soft pine disc 
3 or 4 cm. in diameter and 1 cm. thick fix a 20 cm. 
handle of hard wood. The whole should be given a dead 
black surface, India ink is good for this purpose. Upon 
the disc one may fix with a pin the test object : a circle 
or a square or other form in white, yellow, green, blue 
or red. 

Each blackboard chart must be provided with a rest 
or contrivance to insure that the subject's eye is 20 cm. 
from the surface of the board. Whether this takes the 
form of a rod of wood extending out from the board and 
so adjusted that when the subject rests the most promi- 
nent infra-orbital region upon its end, the cornea will be 
20 cm. from the center of the chart; or whether it takes 
some other form that insures the same result is of little 
consequence. 
j. Experiments and Observations. 

In all the observations which are subsequently indi- 
cated, it is taken for granted that the visual axis is per- 
pendicular to the surface of the chart, that the center of 
the'chart is the point of fixation, and that the accommo- 
dation is kept uniform, i. e., the eye is either uniformly 
focused on the pole of the blackboard perimeter or uni- 
formly relaxed; further that the eye not under observation 
be closed or closely shaded. 

(1) Examine the upper median quadrant by sweeping a 
white circle or square around arc. 60°, keeping the test 
object as near the surface of the chart as possible. If 
the subject does not see it at all, try latitude 50°. Hav- 
ing located the circle which seems to be near the boun- 



VISION. 229 

dary, locate upon each meridian a point which indi 
cates the limit of indirect vision in that direction. Join 
with a continuous line the points located, thus inclos 
ing an area of indirect vision. 

(2) Test the lower median quadrant in the same way. 
Is the total area covered by indirect vision in this 
quadrant greater or less in extent than that in the 
upper quadrant? 

(3) Test the upper-lateral quadrant and then the 
lower-lateral quadrant. Are these two quadrants 
practically equal ? 

Is there any ready explanation why the outer two 
quadrants should contain such an excess of area over 
the inner two quadrants ? 

(4) To record the perimeter outline. 

For this purpose one should have printed charts like 
the one given in Fig. 33. Note that here the circles 
are equidistant. They represent concentric arcs of a 
quadrant with 10° of the circle between each two, 
while the circle upon the blackboard-chart represent 
a radial projection of these arcs upon a plane tan- 
gent to the sphere at the point of fixation. 

In transcribing the perimeter upon the record chart 
one has only to locate the twelve or more points lo- 
cated upon the observation chart and join these points 
into a continuous perimeter. 

Point x, Fig. 30 for example, would naturally fall at 
x' Fig. 31; point y corresponds to y'; Z to Z' whose 
reading is : " Upper-lateral quadrant arc 64°, 70° 
from vertical. 

(5) In the above experiment we have determined the 
perimeter for light sensation only; the subject be- 
ing conscious simply of a light or white spot on a dark 
ground but not certain whether the spot is circular or 



230 



LABORATORY GUIDE IN PHYSIOLOGY. 



square. Determine now the form perimeter, i. e., the 
limits of the field within which a circle can be defi- 
nitely differentiated from a square or triangle. 

Chart the form-perimeter •, i. e., transcribe the peri- 
meter upon the record chart. Is it similar in general 

o 




Fig. 33. 

Fig. 33. Perimeter chart for recording the limits of indirect vision for 
light, for color, and for form. 

form to the light perimeter ? Is it much smaller in area ? 
Determine and chart various color-perimeters : (a) 
yellow; (b) red; (c) green and (d) blue. 



VISION. 231 

Have the color-perimeters the same general form 
as the light-perimeter? If not, describe any noticea- 
ble variations. Which of the color-perimeters incloses 
the greatest area? Enumerate them in order of area. 
Is this the order which one would expect? Give 
grounds for position. 

(7) Take corresponding perimeter for the other eye. To 
use the same blackboard it will be necessary to turn it 
the other edge up. In what general respect do the 
perimeters of the right eye differ from those of the 
left? 

(8) With the help of the light or form-perimeters of 
the right and left eyes, determine the field of binocular 
vision. Is this the field of binocular direct vision or 
binocular indirect vision ? 



LI. Determination of normal vision, a. The acuteness of 

direct vision, b. The range of accommodation. 

c. The amplitude of convergence. 

a. The acuteness of direct vision. 

/. Appliances — Charts printed with Snellen's test type; 
astigmatic chart; test lenses of following strength: 
+.50 D., +.75 D., + 1.00 D., +2.00 D., + 3.00 D., 
— .50 D. 5 — .75 D., — 1.00 D., — 2 00 D., — 3.00 D., 
+ 1.00 D. cyl., + 2.00 D. cyl., — 1.00 D. cyl. — 2. D. 
cyl.; simple test frames, and shade; a photometer; Holm- 
gren's worsteds. 
2. Preparation. — Preparatory to testing normal vision it is 
necessary to make a few general statements regarding: 
(1) The numeration of lenses. 

The refractive power of a lens is the reciprocal of its focal 
distance. The refractive power of a lens whose focal 
distance is 1 m. is, for example, only one-half as great 
as that of a lens whose focal distance is 0.5 m. Mon- 
oyer introduced the term dioptre as a unit in measur- 
ing lenses. One dioptre — (1 D.) — represents the 
refractive power of a lens whose focal distance is 1 
m.; 2 D. corresponds to ^ m.; 3D. to ]A, m.; 4 D. to 
% m., etc. 0.5 D. represents the refractive power of 
a lens of 2 m. focal distance; 0.25 D. of 4 m. focal 
distance, and 0.125 D. of 8 m. focal distance. If the 
lenses are convex (bi-convex) a plus sign is prefixed 
to the number, i. e., + 5 D., means a bi-convex lens of 
5 dioptres refractive power, or \ m. focal distance. 
While — 5 D. means a bi concave lens of \ m. negative 
focal distance. 

232 



VISION. 233 

The use of cylindrical lenses is frequently necessary. 
A cylindrical lens is a section of a cylinder parallel to 
its axis. Cylindrical lenses may be convex or concave. 
A convex cylindrical lens capable of bringing rays to a 
linear focus at a distance of one half meter would be 
designated as follows: -f- 2 D. cyl. 
(2) Test types and visual angle. 

The visual angle is that included between lines joining 
the extremities of an object and the nodal point, or the 
angle subtended by an object, at the nodal point. In 
Fig. 29 the object at d subtends the angle v, while 
the object at D though much larger subtends the same 
angle v. Now it has been determined by Snellen that 
the normal eye distinguishes letters subtended by an 
angle of 5 minutes. If we let d = distance of object 
from nodal point, n = distance of image from nodal 
point, i length of image and o of object, then: 

(1) i : o : : n : d; 

(2) o=id; 

(3) buti=2!Si = tan. v; 

V > II COS V , 

(4) . •. o =d tan. v, 

The tangent of 5' = 0. 001454; assume d = l m (1000 
mm.); what is the height of the smallest letter dis- 
cernible to the average normal eye at that distance? 

At 1 m. height of letter, o = 0.001454X 1000= 1.45 
mm. 

Determine the height of the letters for each of the 
following distances respectively: 60 m., 30 m., 20 m., 
15 m., 12 m., 9 m.,6 m., 4.5 m., 3 m., 2.5 m.,2 m., 1.5 
m., 1 m., 0.75 m., 0.50 m. 

What is the size of the image in all these cases? 
A cultivation of the visual power of the eye may 
readilv in the emmetropic eye bring up its definition 



234 LAB OR A TOR V G UIDE IN PH YSIOL OGY. 

to % above the average or so that the minimum visual 
angle for acute vision equals 4\ What is the size of 
the image when it subtends an angle of 4'? The test 
letters are made with the width of the strokes | the 
height of the letter. What is the width of the retinal 
image of one of the strokes?* 
j>. Experiments and Observations. 

(I) To test the form sense, — In all of the tests here de- 
scribed it is understood unless otherwise stated that 
the subject sit directly facing the chart which should 
be six meters distant, and well illuminated. 

(1) Let the subject put on the test frames with the 
left eye shaded, and direct the right eye to the let- 
ters of the line marked 6 m. These letters in their 
vertical dimension subtend an angle of 5'. The 
average normal eye will be able to recognize 
easily every letter in the line. Should there be any 
hesitation in the differentiation of C from G, of P 
from D or F, of K from X, etc., make a note of it; its 
significance will be apparent later. 

Now in recording the acuteness of vision one com- 
pares the minimum angle of distinct vision in the 
subject under observation with the normal. If the 
subject reads readily at 6 m. the type that is normal 
for 6 m., he is credited with normal vision or with a 
minimum visual angle normal or unity. This is ex- 
pressed in the following manner: Let V equal visual 
acuteness; d, the distance from chart; D, the dis- 
tance at which the type should be read: V = ^ . In 
the above case V=g- or 1, i. e., normal vision. 

(2) Suppose that the subject cannot read the 6 m - 

* The size of the cones of the macular region varies from 0.0033 
to 0.0036 mm. in diameter. 



VISION. 235 

line readily, let him try the line above. If he 
reads that readily his visual acuteness would be: 
V =~=~; two-thirds normal. It is usual, however, 
not to reduce the fraction but to use 6 for the nume- 
rator always. 

(3) How shall one express visual acuteness for an in- 
dividual who reads at 6 m. what he should read at 
21m.? At 24 m ? At 30 m.? At 4.5 m.? At 3 m.? 

(4) How many members of the class have a visual 
acuteness greater than unity? May a visual acute- 
ness above the normal be attributed in any degree 
to cultivation of the vision, or is it to be interpreted 
solely as a natural endowment? 

(5) Make upon a white card with india ink a series of 
vertical lines 1 cm. apart, beginning with a line of 
1 mm. breadth, and decreasing gradually to a hair 
line; place the card upon a blackboard 6 m. distant; 
let a subject with high visual acuteness say how 
many of these lines he can see. 

With dividers and rule measure the breadth of 
the finest of the lines seen. What is the visual 
angle of that breadth? What is the breadth of the 
retinal image of the line ? Can the subject see the 
same number of lines when they are horizontal? If 
not, how may the fact be accounted for? 

(6) If it be found that the subject cannot see clearly 
the largest letters upon the test chart let him move 
to a shorter distance. 

Suppose that he sees clearly the 30 m. type at 2 
meters, what is the value of V? How far would he 
be able to read the 6 m. type ? At what distance 
would he probably have to hold a book whose type 
has a height of 1.8 mm.? 
(1) {a) Let a subject take the seat, 6 m. distant 



286 LAB OR A TOR Y G UJDE IN PH YSIOL O G Y. 

from the chart. Hold before his eye a +0.75 D. 
lens, it will probably make indistinct and blurred 
distant objects which were, without the lens, clear. 
If such be the case it is likely that refraction of the 
eye is normal and for our purpose it may be re- 
corded as an emmetropic eye. 

(3) If, however, the vision remains perfectly clear 
for distant objects, with the +0.75 D. or the +1 D. 
lens before the eye it is evident that the refraction 
of the eye is not normal. 
(c) Suppose, on the other hand, that distant objects 
cannot be clearly seen with the unaided eye; but, 
with the help of concave lenses, clearly seen, it is 
evident again that the refraction of the eye is ab- 
normal. 

(8) In case (7 c), where were the parallel rays 
focused when the concave lens was used ? Where 
were the parallel rays focused in the unaided eye ? 
Would it be possible for the condition to be cor- 
rected by an exercise of the accommodation? If 
the punctum remotum is 2 m., and if the refractive 
indices and curvatures of the refracting surfaces are 
all normal, in what way must the eye differ from the 
normal eye ? This condition is called nearsighted- 
ness or myopia., 

(9) In case (7 b), if a subject can read all of the letters 
expected of the normal eye one credits him with 
V=-|; but, the eye may have accomplished the re- 
sult at the expense of more or less effort. 

If the eye have a punctum remotum beyond infin- 
ity; i. <?., if the rays of light from a distant object 
are not yet converged to a focus by the time they 
reach the retina in the resting eye it will require a 
certain effort of accommodation to produce a clear 



VISION. 237 

image. Such is the condition in the far sighted ^ per- 
son, the condition is called hyperopia. The term 
farsightedness does not mean that the subject can 
see farther than the average individual but that he 
can see far more easily than near. If a subject with 
V= g can see as clearly or more clearly when the 
+0.75 D. lens is in front of the eye there is no 
reasonable doubt that hyperopia in some form is 
present. 

(10) Let the subject direct the line of vision toward 
the center of the chart for testing astigmatism. It is 
probable that not all of the radiating lines will appear 
equally clear cut and black, for most persons have a 
small degree of astigmatism. If the lines are unequal- 
ly clear, where are the clearest ones located? Do they 
describe a diameter across the circle ? If so, 
describe the location of the clear diameter, 0° — 180° 
being the horizontal diameter, and 90° — 90° the verti- 
cal one. 

(11) {a) If the subject has normal vision with no 
astigmatism or normal vision despite a slight as- 
tigmatism, he may be given a better conception 
of just what a moderate degree of astigmatism is 
by putting a^ 1 D. cyl. lens before his eye; or a 
rather high degree of simple astigmatism by try- 
ing a + 2 D. cyl. or + 3 D. cyl. 

(3) How may the subject be made artificially hy- 

peropic ? 
(<r) How, artificially myopic ? 
II. To test the light sense. 

With the photometer test the subject's power to deter- 
mine the difference in the illumination of the two discs 
of the instrument. 



238 LABORATORY GUIDE IN PHYSIOLOGY. 

III. To test the color sense. 

Let the subject take the three test colors : light 
green, purple and red, and choose from the mass of 
worsteds the colors which he considers similar ones, 
placing the chosen color in the class to which it be- 
longs. It is not difficult to determine whether or not 
the subject has a normal color sense. If, for example, 
he is red blind he will not see the red in the purple, 
or related colors, but will classify these with the blues, 
while the reds will be confused with the greens. 
b. The range of accommodation. — The amount of 
refractive change induced by the eye in adjusting for its 
punctumproximum after it has been at rest, i. e., after it 
has been adjusted for its punctum remotum, is termed 
the range of accommodation. In a previous chapter 
the punctum proximum and punctum remotum were deter- 
mined. It was reserved for this place to express the 
position of these limits of accommodation in terms of 
dioptres, and thus most readily determine and definitely 
express the range in simple dioptres. The relation of 
this to what has just preceded will be evident. 

Let R represent the distance of the punctum remotum 
from the eye, then the refraction at rest or the static re- 
fraction r equals the reciprocal of the distance: 

' (0 *=■-£• 

Let P be the distance of the punctum proximum from 
the eye, then the maximum refraction of the eye, p 
equals the reciprocal of the distance: 

(2) P = \- 

When R = oo, ~ = 0, i. e., static refraction equal zero. 
When P =}i meter, ~ — 8. 



VISION. 239 

Let A equal the range of accommodation; Donders 
expressed the range of accommodation thus: 

Take an example: Let the punctum remotum be 50 
cm. (J^ m.) from the eye, the punctum proximum 
10 cm. (j 1 ^ m.); substitute the distances expressed in 
meters in formula (4) and one obtains A = \ m. The 
range of accommodation, i.e., the accommodative power 
of the eye is equal to a lens of \ m. focal distance. But 
a lens of \ m. focal distance is an 8 dioptre lens. A much 
simpler way of arriving at this result is to use: 

r (= -g) and p ( = -p)- If we let a = — , then we may 
write: 

(5) a = p — r. 

To apply this formula to the above example we have 
a — io D. — 2 D. = 8 D. 
I. Experiments and Observations. 

(1) Determine the range of accommodation for each 
member of the class. 

{a) Determine punctum remotum and punctum proxi- 
mum. 

(£) Record these quantities in meters. 

(c) Substitute these values in formula (5) expressing 
the distances in the corresponding dioptres, i. e., 
using the reciprocals of the distances. 

(2) Range of accommodation in myopia. 

{a) Is r positive or negative in myopia ? 

(3) Is a always less than p, or may it sometimes be 

greater? 
(V) What is the average range of accommodation of 

the myopes of the class ? 



240 LAB OR A TOR Y G VIDE IN PHYSIOL OG Y. 

(3) Range of accommodation for emmetropia. 
{a) What is the value of R in emmetropia? 
f?) What is the value of r in emmetropia? 
(r) What is the relative value of a and p in this class 
of cases ? 

(d) What proportion of emmetropes in the class? 

(e) Have they all the same range of accommodation ? 
(/) Can any probable cause be assigned for any varia- 
tions which may be found ? 

(g) How does the average range for emmetropes com- 
pare with the average range for myopes ? 
(4 ) Range of accommodation for hyperopia. 

{a) If the punctum remotum is " beyond infinity" (!) 
that is equivalent to saying that the eye at rest does 
not focus parallel lines (from infinity) upon the 
retina, but the lines must be more than parallel, i. e., 
from beyond infinity; or, better, convergent; but if 
they are convergent they would meet behind the 
cornea. The p. r. for hyperopes is then nega- 
tive in direction and is equal to the distance, 
behind the cornea, at which the convergent lines 
would meet if prolonged. It follows that ^ is in 
the case of hyperopes negative. Our formula (3) 
would then take the form: 

v° J A P V R ^ P ~ R 

Therefore, formula (5) becomes (5') a = p -}- r. 
Now, in determining r one may use a convex lens 
of such a strength as to give the rays the requisite 
convergence. The value of the lens in dioptres is, 
of course, the value of r. In the hyperope a is 
always greater than p. As the determination of the 
punctum remotum of the hyperopic eye is a matter 



VISION. 241 

for the clinician to deal with, we will omit its deter- 
mination here. 

(b) If a member of the class wears glasses having the 
following formula for the right eye, +2D, and if his 
punctum proximum is 12.5 cm. distant from the 
cornea, what is his range of accommodation ? 

(7) What is the range of accommodation of those 
hyperopes in the class whose punctum remotum 
may be determined from the lenses which they use? 
(</) May variations in range be accounted for? 
(e) Is the average range greater or less than that for 
myopes? For emmetropes ? 
(5) Tabulate the values of p and of r for the class, first, 
with respect to age, arranging in the first column all 
of the cases which range between eighteen and twenty 
years, in the second column twent)-one to twenty- 
three, and so on. Determine the average for p and 
for r from each age column. 
(«) Does age within the limits of your table affect 

the punctum proximum ? If so, how ? 
(£) Does age affect the punctum remotum as shown 
by your table ? 

(c) If the volume of data justifies it, make a chart 
showing the effect of age upon the range of accom- 
modation. Use the age units for divisions of the 
axis of abscissas, and dioptre units of p and r for 
the divisions of the axis of ordinates. 

The amplitude of convergence. — The fact of the con 
vergence of the visual axes of the two eyes in binocular 
vision has been demonstrated in a previous lesson. We 
come now to the measurement of this function. 

To measure convergence. — To get a clear conception of 
the situation, let us call the line which joins the centers 
of rotation of the eyes the base line, A plane perpen- 



242 LABORATORY G UIDE IN PH YSIOL OGY. 

dicular to the middle of the base line may be called the 
median plane. Any point in this plane which is fixed by 
the two eyes in binocular vision may be called the point 
of binocular fixation. The line joining this point to the 
middle of the base line would lie in the median plane, 
and would be called the median line. 

If the point of fixation be at a great distance (infinity) 
the lines of fixation of the two eyes would be parallel to 
the median line. In this case there would be no con- 
vergence. If, however, the point of fixation be near there 
will be a convergence of the two lines of fixation toward 
that point. The amount of convergence is greater the 
nearer the point, and is called the angle of convergence. 
The angle of convergence is then the angle between the 
line of fixation at infinity and the line of fixation at the 
given distance less than infinity, the given distance be- 
ing measured on the median line, beginning at the base 
line. 

The geometric situation is indicated in the accom- 
panying figure (Fig. 34). Let C represent the center 
of rotation of. the left eye, M the middle of the base line 
and the origin of the median line; CP the line of fixa- 
tion of an object at infinity; MM' the median line; the 
line CM is one-half the base line; represent the distance 
CM by b. The angle D'CP is the angle of convergence 
when D' is the point of binocular fixation. As 
to the exact measure of the angle, it is evident from 
the figure that the line MD', which we may represent by 
d, is the cotangent of the angle of convergence (ang. c). 

The unit of measurement for the angle of convergence 
is the meter angle (Ma) of Nagel. The meter angle is 
the angle of convergence when the point of binocular 
fixation is 1 m. distant (d = l,000 mm). Ma equals the 
angle whose cotangent is ~ (cot Ma=J). The aver- 



VISION. 



243 



age base line being 64 mm., the average Ma may be 



thus expressed: Cot Ma= 1 |°; Ma=l 



50' 



It is not 



customary to use in practice the absolute values for the 
angles, but a convenient series of approximate values 
suggested by Nagel. 

If d = 500mm. (^m.), ang. c = 2 Ma; if d = yi m., 





Fig. 34. 

Fig. 34. For description 
see LI=C. 



Fig. 35. 

Fig. 35. For description 
see Ll=c=(5). 



ang. c = 3 Ma. If d — f£ m., the accommodation = 4 D 
and angle of convergence = 4 Ma. 

Besides the convenience of this system, it indicates 
at once the direct relation between accommodation and 
convergence. 

The amplitude of convergence is the total number of 



244 LAB OR A TOR Y G U1D E IN PH YSIOL O G Y. 

meter-angles of convergence which the individual can 
call into play. It is the difference between the punctum 
proximum of convergence [p c ] and the punctum re- 
motum of convergence [r c ] expressed in meter angles; 
which are really the reciprocals of the distances. This 
may be thus expressed: 

0) rc = Fc — si in distances > or ; 

(2) a c = p c — r c in meter angles. 

Experiments and Observations. — Let each member of the 
class be in turn the subject of examination. 

(1) Determine the pupillary distance, i. e., the distance 
from the center of one pupil to the center of the other 
when the eyes are fixed on a distant object. One-half 
of this is approximately equal to b, and in the experi- 
ments which follow may be used as such. 

(2) Take a board 1 m. in length and 10 cm. in width. 
Along the middle of one side draw a line which may 
represent the median line; graduate the line in 
decimeters; the proximal % m. may be graduated in 
centimeters. At each centimeter or decimeter bore a 
small hole into which a post may be set. Make two 
posts about 5 cm. or 10 cm, in height; into the top of 
one set a needle, split the top of the other so that it 
will hold a card printed with fine type (not to exceed 
1 mm. in height, finer if possible). Support the 
board so that it shall be in a horizontal plane and 
5 cm. or 10 cm. below the eyes. 

(3) To determine the punctum proximum of convergence: 
{a) Let the subject sit so that the line on the board 
shall be in the median plane and parallel to the 
median line; let him look at the needle when the post 
is set at 1 m. Supposing that his punctum remotum 
is at infinity, what is the ang. c? 



VISION. 245 

( b) Let the subject look in turn at the needle when 
the post is set at 50 cm.; at 40 cm.; at 30 cm.; at 
25 cm.; at 20 cm.; what is the ang. c in each case, 
expressed in meter angles ? 
(7) From this point if the needle appears perfectly 
clearly denned move the post up toward the eyes 
1 cm. at a time as long as the vision is binocular 
and the image single. 

As soon as the image is double one may be cer- 
tain that the eyes are no longer able to converge 
sufficiently to bring the images upon corresponding 
points of the retina and that the punctum proxi- 
mum of convergence (p c ) has been passed. Find 
the nearest point at which the image is single — the 
nearest point at which the fine printing on the card 
is perfectly clear; this is the punctum proximum of 
convergence (p c ). 
(*/) Determine the punctum proximum of conver 
gence for each individual in the class. 
(4) To determine the punctum remotum of convergence (r c ). 
If the eyes can be directed parallel but cannot 
diverge, the punctum remotum may be expressed as 
follows: i c = ^ — -^ =0. Landoldt says, however, 
that "the majority of normal eyes can diverge more 
or less," i. e., there is a negative convergence ( — r c ). 

The formula — (2) . . . a c = p c — r c becomes 
a c = p c — ( — r c ); or 
(2'). . . a c = p c -f-r c 

Let it be noted that in this case the value of r c 
cannot be determined by carrying the object to a 
greater distance, but recourse must be had to abduct- 
ing prisms, i. e., prisms whose apices are turned away 
from the median line. The negative convergence may 



246 LABORATORY GUIDE IN PHYSIOLOGY. 

be determined by finding " the strongest prisms which 
a person can overcome"; while seeing a distant object, 
without double vision. The deviation of a prism may 
be taken as half the angle of the prism; a No. 6 prism, 
produces a deviation of 3°. If only one prism be 
used the 3° is divided equally between the two eyes. 
Let it be understood that two prisms of equal angle be 
used. 
(5) To compute the ang. c in meter- angles for any prism and 
any length of base-line. 

Let n equal the angle of deviation, i. e., one-half the 
number of the prism. Let b equal one-half the base- 
line. Let d equal the distance of the punctum re- 
motum, to be computed. Then, 

(1) b : d : : sin n : cos n (see Fig. 35). 
(3)....d = b.^=bcotn. 

But the punctum remotum of convergence (r c ) ex- 
pressed in meter-angles, is found by dividing lm. by 
d, therefore 



(3)....r c - 



b cot n 

If a person whose base-line is 64 mm. is able by 
divergence to overcome a pair of No. 6 prisms his 
punctum remotum of convergence would be negative 
and equal to 1.63 Ma. Determine the punctum re- 
motum of convergence for each individual in the class. 

(6) Determine the amplitude of convergence for each 
member of the class using the formula; a c =p c — r c . 
Tabulate the results. 

(7) Compare this table with the one in which the range 
of accommodation is recorded. Is< there any parallel- 
ism in the variations of accommodation and conver- 
gence ? Does age seem to have any appreciable influ- 
ence upon the amplitude of convergence ? 



OPHTHALMOSCOPY AND SKIASCOPY. 
By ALFRED M. HALL, A. M., M. D. 



LI I. Normal ophthalmoscopy, direct method. 

Gould defines ophthalmoscopy as, "the examination 
of the interior of the eye by means of the ophthalmoscope." 
Normal ophthalmoscopy is the examination, by means of 
the same instrument, of the normal eye or a model of 
the normal eye. 

/. Appliances. — An ophthalmoscope, with concave mirror; 
dark room; lamp; and Thorington's skiascopic eye or an 
equivalent. 
2. Preparation. — Arrange the model and the lamp so that 
they will be in the horizontal plane with the observer's 
eye. Place the skiascopic eye directly in front of the 
observer's eye, and the lamp a little to one side of the 
model. 
j. Operation. — Let the observer hold the ophthalmoscope 
with the right hand, mirror forward, close to the eye, 
directing the vision through the hole in the instrument. 
Throw the light, reflected by the mirror, into the skia- 
scopic eye. Find the red reflection of the fundus, then 
gradually lessen the distance between the observer's eye 

247 



248 LAB OR A TOR Y G UIDK IN PHYSIOL OGY. 

and the model to about 2 or 3 cm. The skiascopic 
eye will then be illuminated and the fundus with its 
structures will be clearly defined. 
4.. Observations. 

a. Adjust the model to represent the emmetropic eye. 

(1) Determine, with the ophthalmoscope, the color of 
the fundus. Enumerate the structures seen. 

(2) Describe the papilla, or entrance of the optic 
nerve. Is the papilla in the visual axis or to one 
side of it ? Describe its position with respect to 
the visual axis of the eye and determine the most 
advantageous position of observer, model and in- 
strument to get a direct view of the papilla in the 
right eye; in the left eye. 

(3) Describe the location of the arteria and vena 
centralis retinoe with reference to the papilla. 

(4) The ring formed by the border of the papilla is 
sometimes called the scleral ring or the choroidal ring. 
Can this ring be distinctly seen ? 

(5) The macula lutea and the fovea centralis are the 
most sensitive portions of the retina and are in a 
direct line with the visual axis of the eye. 

What is the most advantageous position of model,, 
observer and instrument in order to get a direct il 
lumination of this part of the fundus? Describe 
the appearance of the structures in question. 

(6) Describe the retinal blood vessels minutely; 
drawing a map of their distribution. 

b. The observation of the retina in t'he hyperopic eye. 
Adjust the model for three dioptrics of hyperopia. 

(7) Are the retinal blood vessels distinct when the 
above described method of observation is used? 

(8) Place in the rack, before the model eye, the follow 



VISION. 249 

ing lenses, with each one testing for a distinct reti- 
nal image : 

*± 1 D., + 2 D., + 3 D., and+ 4 D. 
With which one of the lenses is the clearest 
image obtained? Are all of the images of equal 
size? Explain, giving a figure.* 

(9) In hyperopia do the rays focus in front of, on, 
or behind the retina? What direction do the rays 
take after leaving the hyperopic eye from the illu- 
minated retina? Are they parallel, divergent or 
convergent ? 

Observation of the retina in a myopic eye. 
Adjust the model for myopia, e. g., three dioptrics. 

(10) Are the retinal blood vessels distinct? 

(11) What direction do the rays from the retina take 
on emerging from the myopic eye, divergent, con- 
vergent, or parallel? 

(12) In which of these three cases would the normal 
eye be able to get a clear image of the retinal struc- 
tures ? 

(13) In which case would a correcting lens be neces- 
sary? Should one use a convex or a concave lens ; 
and why ? 



*In all work with the ophthalmoscope or retinoscope it is under- 
stood that the observer's eye is emmetropic, either by nature or by cor- 
rection, and that his accommodation is suspended. One may get a clear 
view of the retina without fulfilling these conditions, but one cannot 
draw reliable optical conclusions. 



LIII. Normal ophthalmoscopy, indirect method. 

/. Appliances. — The same as in exercise LII, with the addi- 
tion of a lens of -f 12 D. to + 20 D. 

2. Operation. — With the model or eye to be observed, the 
light and the observer arranged as in exercise LII, 
direct the light reflected by the mirror into the observed 
eye and find the red reflection of the fundus of the eye. 
Hold the lens between the thumb and index finger and 
place it directly between the mirror and the eye under 
examination, and at a distance from the latter of 6-8 cm. 
Be careful that the center of the lens corresponds to the 
center of the pupil and that the plane of the lens is per- 
pendicular to the line of vision. 

j. Observations. 

a. Observation of the emmetropic eye. 

(1) The rays of light emerging from the observed eye 
are focused by the convex lens, which the observer 
holds, and form an aerial image of the retina. If 
a -|- 12 D. lens be used, and if its optical center be 
held 8 cm. from the anterior, surface of the cornea, 
how far from the cornea will the aerial image be 
formed? 

(2) Trace in the image all of the structures enumer- 
ated in the direct method. Is the image erect or 
inverted ? Is the field larger or smaller than one 
sees in the direct method? Are the structures mag- 
nified or the reverse? Account for all phenomena, 
representing the optics of the case with a figure. 

(3) Does a change in the distance between the cornea 
of the model or eye and the lens which the observer 

250 



VISION. 251 

holds alter the size of the image ? Account for 
observation. 

b. Observation of the hyperopic eye. 
Adjust the model for 3 D. of hyperopia. 

(4) Does an increase of the distance of the lens from 
the cornea cause the image of the papilla to be 
altered in size? Account for all phenomena. 

c. Observation of the myopic eye. 

Adjust the model to represent 3 D. of myopia. 

(5) Does the increase of the distance of the lens from 
the eye cause the image of the papilla to become 
altered in size or reversed in position ? Account for 
all phenomena. 

(6) If the position of the -|- 12 D. lens which the ob- 
server holds remain the same — 8 cm. from cornea — 
will there be any variation in the distance from the 
cornea of the retinal image for the hyperopic eye 
and myopic eye ? 

Will the distance for the hyperopic eye be 
greater or less than for the emmetropic eye ? Why ? 
Will the distance for the myopic eye be greater or 
less than for the emmetropic eye ? Why ? 

d. Observation of the human eye. 

At this point in the student's work, let him practice 
the direct and indirect method of ophthalmoscopy 
upon his comrades, after two or three days of practice 
he may pass to the following exercise. 



LIV. Skiascopy, 

Gould defines skiascopy as " a method of estimating 
the refraction of the eye by observation, through the 
ophthalmoscopic mirror, of the movements of the retinal 
images and shadows." Synonyms: Fundus reflex test; 
umbrascopy; pupiloscopy; koroscopy; keratoscopy; ret- 
inoscopy, etc. 

i. Appliances. — A simple retinoscope or an ophthalmos- 
cope with a plane mirror; Thorington's skiascopic eye 
or an equivalent; dark room; lamp; etc. 
2. Operation. — The observed eye and lamp are to have 
the same relative position as in ophthalmoscopy. Let 
the observer sit directly in front with the eye in the 
same horizontal plane with the lamp and observed eye, 
and somewhat more than 1 m. distant from the observed 
eye. Throw the light reflected by the mirror into the 
observed eye; rotate the mirror slowly and a shadow will 
be seen in the pupil of the observed eye. 
J. Observations. 

a. Observation of the emmetropic eye. Adjust the model 
to represent emmetropia. 

( 1 ) Does the shadow move in the same direction as the 
mirror rotates or in the opposite direction, i. e., does 
the shadow move "with the mirror" or "opposite?"" 

(2) Is the movement of the shadow quick or slow. 

b. Observation of the myopic eye. 

(I) Adjust the model to represent less than 1 D. of 
myopia. 
(3) Note that the shadow movement is with the 

252 



VISION. 253 

direction of the mirror rotation and that it is rela- 
tively quick. 
(II) Adjust the model to represent a myopia of more 
than 1 D. 

(4) Note that the shadow movement is opposite the 
direction of the mirror rotation and that it is quick 
when the myopia is of low degree, slow when of 
high degree. 

(5) Observe alternately the three conditions indi- 
cated above until their differences are so familiar 
that any one of the conditions may be readily and 
unerringlydetected by the observer when they are 
arranged for him by the instructor. 

Observation of the hyperopic eye. 

Adjust the model to represent any degree of hyper- 
opia. 

(6) Note that for a low degree of hyperopia the 
shadow movement is with the mirror rotation and 
quick. 

(7) Note that for higher degrees of the condition the 
shadow movement is with the mirror and slow. 

(8) How may one differentiate a high degree of 
myopia from a high degree of hyperopia ? 

(9) Is there any difference in the size, shape, dis- 
tance or position of the shadows in these two condi- 
tions ? 

Observation of the human eye. 
Let the student practice upon his comrades. 

Note: Observation of the astigmatic eye is inten- 
tionally omitted here. It belongs more espcially to the 
clinical phase of the subject. 



PHYSIOLOGICAL H/EMATOLOGY. 



G. PHYSIOLOGICAL HEMATOLOGY. 
By W. K. Jaques, Ph. M., M. D. 



INTRODUCTORY. 

The scientific world is constantly giving her discoveries 
to the medical profession to be utilized in diagnosing dis- 
ease and in providing means to relieve suffering. Each fact 
thus obtained is a step nearer to the goal of positive medi- 
cine and removes us farther from the past with its unsatis- 
factory theories and dogmas. 

Blood, the most difficult tissue to study, has at last 
begun to give up its secrets to the patient workers in phys- 
iological and pathological laboratories. Although the facts 
are few compared with the great labor it has taken to obtain 
them, they are of such practical value that no practitioner 
can afford to be without them. 

The discovery that toxins and antitoxins were con- 
tained in the blood serum made possible the production of 
diphtheritic antitoxin and gives us the serum diagnosis of 
typhoid fever, beside opening a wide field of possibilities 
for the future. 

The finding of the plasmodia of malaria is often of the 
greatest value in clearing up an obscure diagnosis. When 
methods shall have been devised which will make their 
detection less difficult, the discovery of the presence of 
bacteria in the blood and the identification of the same will 
be of great clinical importance. 

257 



258 LAB OR A TOR Y G U1DE IN PH YSIOL OGY. 

To understand the appearance of pathological blood, a 
knowledge of normal or physiological haematologyis essen- 
tial. It is the object of the following pages to assist the 
student in obtaining this knowledge and in laying the 
foundation for the study of pathological haematology. 

A knowledge of the microscope and its technique is 
essential and the work of the student should be so arranged 
as to include considerable practice with that instrument 
before entering upon a study of that subject. 

If the practitioner has a fair knowledge of pathology, 
histology and bacteriology, with the help of the following 
suggestions he may take up with profit the subject of 
haematology. 

In class work the blood maybe obtained from students. 
The pain is minimized if the blood is properly obtained, 
and practice on themselves will impress this fact upon the 
students. The general practitioner can get material from 
his patients. 

The technique of haematology can only be acquired by 
practice. The student will secure this more readily than 
the practitioner because his attention will not be dis- 
tracted by diagnostic possibilities. It is well for the prac- 
titioner to go over the whole ground several times for the 
sole purpose of mastering every detail. Unless the tech- 
nical part of the work is correctly and easily done, the 
specimens will be unsatisfactory, the results will be untrust- 
worthy and the knowledge of the subject imperfect. 

The methods here employed are those of the best 
students of haematology with modifications from the ex- 
perience of the author. Although the best to-day, to mor- 
row they may be remembered only as the stepping stones 
to more perfect work. Many truths are yet undiscovered 
in this wonderful river of life — the blood — and the grati- 
tude of a race will be due him who reveals them. 



LV. Examination of fresh blood. 

i. Appliances. — Microscope; one twelfth inch oil- immersion 
lens; 22 mm. cover glasses; slides; saddler's needle and 
holder; clean piece of old muslin one-half meter square; 
paper and pencil. 

2. Preparation. — Clean cover glasses and slides as follows: 
Immerse in 60% acetic acid, then wash in soap and 
water and place in dilute alcohol; just before using, 
wipe dry and place under a bell-jar; the needle should 
be so placed in the holder that it protrudes one-fourth 
to one-third inch. 

A convenient needle-holder, the exact size of which 
is shown in Fig. 36, may be obtained from a dental sup- 
ply house. 



~\l^J±luif.ii)ni li'-f jit,, I, _— . .. ... , ^J 



Fig. 36. 

A medium saddler's needle may be obtained from a har- 
ness shop. If too long, it can be broken and the point 
used. These needles have three cutting edges so that 
blood flows easily from a puncture made by one. 
Operation. — Wipe the lobe of the ear with a damp 
cloth; then briskly with a dry cloth; seize the lobe 
with the left finger and thumb quite tightly; thrust 
the needle into the ear with a quick stroke. Wipe 
away the first drop; then when the second drop has 
become a little more than one-eighth of an inch across 
its base, bring the center of the cover glass under 
the drop and touch the lower part without touch- 

259 



260 LABOR A TOR V G UIDE IN PHYSIOL OGY. 

ing the ear as shown in Fig. 46. Quickly place the 
cover glass, blood-side down on a clean slide and exam- 
ine. 

4. Precautions. — Cover glasses must be clean, dry and free 
from dust. The blood must be collected quickly or it 
will form rouleaux. A warm stage prolongs the normal 
appearance of the blood. Placing the microscope in 
the incubator at body temperature for half an hour before 
using will keep the slide warm for some time. In adjust- 
ing the needle for puncture the condition of the patient 
should be considered. A full blooded patient will require 
a smaller puncture than an anaemic one. 

5. Observations. — Note that the red corpuscles are round 
in shape. As the plasma dries, it causes currents; as 
the corpuscles float in these they strike each other, dent, 
elongate and act like bags of jelly, returning to their 
round shape when free. 

a. Red corpuscles. 

(1) Note biconcavity; what causes it ? 

(2) Are there variations in the size of the red cells? 

(3) What is crenation? Note when it begins. 

(4) Do you see two motions of red corpuscles ? De- 
scribe any motion seen. 

(5) Do you see small motile bodies in the plasma? 

b. White corpuscles. • 

(6) How do white corpuscles differ from red ? 

(7) Do they float as easily in the blood current? 

(8) How do they compare in size with red corpuscles ? 

(9) Why are white corpuscles smaller in fresh blood 
than in dried specimens ? 

(10) What movements do you see? 

(11) Do you see any variation in size? 

(12) In which kind do you see the amoeboid move- 
ments? 



PHYSIOLOGICAL HEMATOLOGY. 



261 



(13) Do you see some white corpuscles with large 
granules ? 

(14) What is the approximate ratio of the white cells 
to the red ? 




Fig. 38a. Thoma-Zeiss blood-corpuscle counter. 



LVI. Counting red corpuscles. 

7. Appliances. — -Microscope with one- seventh inch objec- 
tive, and a mechanical stage; needle and holder; Thoma- 
Zeiss counter. 

2. Preparation. — (1) The counter and pipette should be care- 
fully cleaned with water, followed by alcohol and thor- 
oughly dried. (2) Prepare the following solution for 
diluting blood : 

Sod. sulph gm. 107 

Aqua dist c c. 120 

j. Operation. — Obtain the blood as described in Lesson LV, 
allowing it to collect until almost ready to drop. Then 
insert point of pipette into the drop and by sucking gently 
draw the blood up to the mark 0.5. Wipe the end of 
the pipette and insert it into the diluting solution, sucking 
it up until the bulb is filled to the mark 101. Close 
ends of pipette with fingers, rolling and shaking it about 
for a minute. Blow out three drops of the diluted blood. 
Then drop from the pipette on the round table of the coun- 
ter just enough of the dilution to cover it when the cover is 
placed upon it without causing any of the liquid to flow 
over into the moat. (Fig. 38b). Place the counting 
slide under the microscope and find the upper left hand 
square; count all the corpuscles in it. Then count the 
next square to the right and continue until all the upper 
row has been counted; write down the number of cor- 
puscles. Then move the counter so that the next lower row 
can be counted from right to left continuing until all the 
squares are counted. Clean the counter; agitate the 

262 



PHYSIOLOGICAL HEMATOLOGY. 263 

pipette, blow out a drop, place the diluted blood on the 
counter and count as before. If the two countings are 
nearly the same, this will be sufficient; if there is much 
difference, a third field should be counted and an aver- 
age taken of the two fields nearest alike. Divide the 
number of corpuscles by the number of squares; multiply 
this by 200 to make up for the dilution and then by 400, 
because each square is equivalent to one four-hundredth 
of a cubic millimeter. This will give the number of cor- 
puscles per cubic millimeter. Count the corpuscles on 



Fig. 38b. 

Fig. 38b. Showing the right and the wrong way to fill a Zeiss count- 
ing cell. a. Too little blood, b. Too much blood, c. The proper 
amount of blood. 

one half the boundary of each square but do not count 
them on the other half. 
4. Precautions. — See that the blood corpuscles are evenly 
scattered over the field. (Fig. 39). If they are clus 
tered, it shows faulty technique and the counting dilution 
must be prepared again with more care. Clean counter 
and pipette first with water and then with alcohol after 
using, being careful to leave the tube perfectly dry. The 
pipette is easily broken. The fine lines on the counter are 
injured by rubbing with a coarse cloth. The cover glass 



264 LAB OR A TOR Y G UIDE IN PII YSIOL OGY. 

should be adjusted before the corpuscles have time to 
settle. 
5. Observations. 

(1) Make counts of red blood corpuscles from several 
apparently normal individuals. 

(2) Is there any appreciable variation in the number 
per cubic millimeter? 



/(VlO ^ 




00- o° \ 

,00 O G§ I 



Fig. 39. 

Fig. 39. a. Successful blood spread with corpuscles evenly distributed, 
b. Poor spread with corpuscles clustered. 

(3) Can the variation be attributed to faulty methods? 

(4) What is the average count for normal individuals? 

(5) What is' the range between maximum and minimum 
observations on the normal individuals observed ? 

(6) Account, if possible, for the variations observed. 



LVII. Counting white corpuscles. 

i. Appliances. — Same as in Lesson LVI with the substitu- 
tion of the large bore pipette. 

2. Preparation. — Cut a square out of a circular piece of 
cardboard which fits in the barrel of the microscope 
with mechanical stage. The square should be just large 
enough to bound the counting square of the counting 
slide. (Fig. 40). Adjust the circular card with the square in 




Fig. 40. 

Fig. 40. Plan of cardboard 
diaphragm for microscope tube. 
For description see LVII-2. 





23 




3 




11 




Zl 


Z 


10 




/ 1 2 * 


I 


•7 


It 




7 


% 


7 


■ .=:-:. 


/o 


// 


/z 


i 


\ t_ 


IS 

1% 


if 


i3 


< 




v 2J 


& 


't 


1ST 






6 









Fig. 41. 

Fig. 41. Showing the sequence of 
the fields counted. For description 
see LVII-3 



it in the upper part of the microscope barrel just below the 
eyepiece. By lengthening and shortening the micro- 
scope the square can be adjusted to the square of the 
counting slide. 
(2) For a diluting solution, use the following : 

Acidum acet c. c. 4 

Aqua dist c. c. 100 

265 



266 LAB OR A TOR Y G UIDE IN PH YSIOLOG Y. 

Operation. — Obtain blood as described in exercise LVI 
and dilute with the above solution. Bring upper line of 
ruled square to bottom of the square of the field; then the 
field of the microscope will correspond to field one in the 
figure. Count all the white cells in the field. Then fix 
the eye on a cell in the upper margin and bring.it to the 
lower edge of the field; count this field and proceed in the 
same way to field 3. Turn stage back to ruled space, us 7 
ing the border to indicate where to begin to count. Count 
fields 4, 5 and 6; turn back to ruled square and proceed 



mmmmm)^ 




Fig. 42. 
Fig. 42. Position of solution tipped to receive pipette horizontally. 

to 7, 8, 9; turn back to ruled square and count 10, 11 and 
12. For a larger count, proceed in the same manner 
from the central ruled space to count the additional 
squares enclosed with dotted lines. The acetic acid in 
the diluting solution renders the red corpuscles transpar- 
ent or dissolves them entirely. If this does not so ap- 
pear, the acid is too weak and more should be used to 
obtain the desired results. 
:. Precautions. — Make a good deep puncture. Have a large 
drop of blood. Remember that the bore of this pipette 
is larger than that of the pipette for red corpuscles and 
the solution will run out if the pipette is held perpendic- 
ularly. (Fig. 42.) The suction also must be more gentle 



PHYSIOLOGICAL HEMATOLOGY. 267 

than with the small bore pipette. Remember to thor- 
oughly clean and dry the pipette after using. 
Observations. 

(1) Estimate the number of white corpuscles per cubic 
millimeter in several apparently normal individuals. 

(2) What is the proportion of white to red corpuscles 
in each individual ? 

(3) Is there considerable variation in number of white 
corpuscles in different individuals? 

(4) Is there considerable variation in the proportion be- 
tween white and red corpuscles in different individ- 
uals? 

(5) What may cause the variation ? 



LVIII. Counting red and white corpuscles. 

/. Appliances. — Microscope with one- seventh objective; 

needle and holder; Thoma-Zeiss counter with small 

lumened pipette. 
2. Preparation. — Prepare the following solution for staining: 

toisson's solution. 

Methyl violet, 5 b 025 gm. 

Sod. chlor 1.000 gm. 

Sod. sulph 8.000 gm. 

Neutral glycerin 30.000 cm. 

Aqua dist 160.000 cm. 

j. Operation. — Obtain blood as described above and dilute 
1 to 200 with Toisson's solution. Place the counting slide 
under the microscope and find the upper left-hand square; 
count the red corpuscles in each square from left to 
right; then retrace the same field and count the white 
corpuscles. Repeat this procedure with the next row of 
squares, continuing the same way until all the squares 
are counted. Write the number of red corpuscles on 
one side of a line, the white on the other. Clean the 
counter; agitate the pipette, blow out a drop, place the 
solution on the counter and count as before. If there is 
much variation between the number of first and second 
field, count a third field and take the average of the 
two fields nearest alike. Divide the total number of 
corpuscles by total number of squares counted; multiply 
by 200 (amount of dilution) and then by 400, which will 
give number of corpuscles per cubic millimeter. The 
use of this staining fluid enables the student to count 



PHYSIOLOGICAL HEMATOLOGY. 269 

both red and white corpuscles at the same time instead 
of counting separately as in Lessons LVI and LVIL This 
is important to determine the relative proportion of red 
to white, or white to red corpuscles. 

4. Precautions. — Extra care must be exercised in cleaning 
pipette after the use of this staining solution. 

5. Observations . 

(1) Compare the results of this method with those 
obtained in counting red and white corpuscles separ- 
ately. 

(2) Determine the proportion of white to red corpuscles 
in a number of normal individuals. 

(3) Has age any influence on the proportion? 

(4) Has sex any influence on the proportion ? 

(5) Has the general condition of the nutrition any in- 
fluence ? 

(6) Is the proportion always the same in one individual? 
If not, is there any periodicity in the changes ? 

(7) Determine, if possible, the causes of the variation. 



LIX. Centrifugalizing the blood. To determine the rela= 
tive volume of red corpuscles and plasma. 

/. Appliances. — Daland's hematocrit (Fig. 43); small rub- 
ber tubing to fit capillary tube; needle and holder; vase- 
lin; white paper. 

2. Preparation. — Adjust rubber to capillary tube. Put 
empty tube in one arm of crosspiece to preserve bal- 
ance. 

j. Operation. — Obtain blood from the lobe of the ear as 
heretofore described. Draw capillary tube full of blood. 
Grease the finger with vaselin and hold over the free 
end of the tube before drawing off the rubber. Place the 
tube in the crosspiece of the instrument as quickly as 
possible and revolve at least two minutes at the rate of 
seventy turns per minute. Take out the tube and lay 
on a piece of white paper to read the divisions. Each 
degree of the scale is estimated to contain about 100,000 
cells; hence, a tube in which the red column stands at 
50 would indicate about 5,000,000 red corpuscles per 
cubic millimeter. The use of this instrument is de- 
signed chiefly to show the volume of red corpuscles rather 
than the number^ as shown by the Thoma-Zeiss counter. 

4 Precautions. — See that the instrument is securely at- 
tached to the table and the crosspiece to the instru- 
ment before setting it in motion. 

5. Observations and Problems. 

(1) Determine the volume per cent of red blood cor- 
puscles in a number of normal individuals. 

(2) Do apparently normal individuals have the same or 

270 



PHYSIOLOGICAL HEMATOLOGY. 271 

approximately the same volume per cent of red blood 
corpuscles. If not, seek for causes for the differences 
in different individuals. 



Fig. 43. 
Fig. 43. Haematocrit. 



(3) Does the same individual have the same volume 
per cent of red blood corpuscles all the while ? 



272 LABOR A TOR Y G VIDE IN PH YSIOLOG Y. 

(a) If there is a variation is there any periodicity to 

be observed ? 
(£) Seek for causes of any variations in the same 

apparently normal individual. 

(4) The volume per cent as recorded by the haematocrit 
varies with the product of two factors ; the average 
volume of the individual corpuscles multiplied by the 
number of corpuscles per unit volume. (V oo v X n) 
{a) Is the average volume of the individual corpus- 
cles (v) necessarily constant? 

(3) If it is not constant, would one be justified in 
drawing conclusions regarding the number of cor- 
puscles per unit volume (n) after observing the 
volume per cent (V) with the haematocrit? 

(5) What variation of the observation as above made 
would enable one to determine with reasonable accu- 
racy the number of corpuscles per cubic millimeter ? 



LX. Estimation of haemoglobin. 

1. Appliances. — v. Fleischl's haemometer; medicine dropper; 
distilled water; needle and holder; capillary tube; lamp. 

2. Preparation. — See that the capillary tube is perfectly 
clean and dry; if there is any doubt, draw a thread wet 
with ether and alcohol through it. Fill one side of the 
metallic cell about one-quarter full of distilled water. 




Fig. 44. 
Fig. 44. Fleischl's Hasmometer. 



j. Operation. — Puncture the ear and obtain blood drop. 
Just touch outside of drop with capillary tube held in 
a horizontal position; it should quickly fill by capillary 
attraction. Carefully and quickly wipe away any blood 



273 



274 LAB OR A TOR Y GUIDE I AT PHYSIO LOG Y. 

that may be on the outside of the tube. Plunge it into 
the well of water, shaking it back and forth to thor- 
oughly mix the blood and water. With the medicine 
dropper wash the tube with a few drops of distilled 
water; then remove the tube and draw the solution in 
and out of the dropper several times to be sure it is 
well mixed. Then fill both compartments to the brim 
with the dropper, taking care that the mixture of blood 
and water shall not flow over into the pure water. Ex- 
clude daylight, and by artificial light adjust the compart- 
ment containing clear water, so that it comes over the 
slip of colored glass. Adjust the reflector so that light 
is thrown up through the well. Then adjust the slip of 
colored glass until it corresponds with the color of the 
diluted blood and read the amount indicated by the 
scale. This will give the percentage of haemoglobin, 
100 being the standard for normal blood. 

Any approximate success with this instrument pre- 
supposes a color sense. Even when this is present in 
the student, the instrument itself is not entirely reliable 
as there is sometimes a variation in the colored slips of 
glass. It is also not reliable for percentages of haemo- 
globin under 20. 
4. Precautions. — The capillary tube should be cleaned by 
drawing through it a thread wet with alcohol and ether. 
The tube must be filled and emptied quickly to prevent 
coagulation. In reading the instrument, do not face 
the light but let it come from the side. The instrument 
should be so placed that the wedge will not move from 
left to right but to and from the operator. Use as little 
light as possible. Use first one eye and then the other. 
Move the screw with quick turns rather than a gradual 
motion, as the impression of a glance is better than a 
prolonged look. 



PHYSIOLOGICAL HEMATOLOGY. 275 

Observations and problems. 

(1) Determine in the cases of several normal individuals 
whether the blood is normal when compared with 
v. Fleischl's arbitrary scale. Let the same observer 
make two or three consecutive tests of the blood of 
each subject.* 

Record for each subject the average of the two or 
three tests made by one observer. 

(2) Account, if possible, for any variations found. 

(3) Do the individuals who show a low haemoglobin 
reading show also a low volume per cent, and con- 
versely ? If so, would one be justified in the conclu- 
sion that the hcemoglobin varies as the volume per cent of 
the red blood corpuscles ? 

(4) Do the individuals who show a low haemoglobin, 
reading, show also a smaller number of red blood cor- 
puscles per unit volume, and conversely? If so, would 
one be justified in the conclusion that the hcemoglobin 
varies as the number of red blood corpuscles per unit vol- 
ume? 

(5) Are there any conditions in which both of these 
conclusions may be consistent with the results of the 
reasoning at the end of the previous exercise, LIX? 



* If the same observer obtained approximately the same reading on 
the second and third test of an individual's blood it may be taken for 
granted that for comparison with each other this observer's readings 
are sufficiently reliable. 



LXI. ine microscopic technique of hematology, a. 
Spreading blood, b. Fixing and staining. 

a. "Making the spread." 

i. Appliances. — Microscope with one-seventh objective; 
needle and holder; square cover glass, \ inch. 

2. Preparation. — Clean six or more cover glasses with di- 
lute acetic acid, soap and water, and alcohol. 

j. Operation. — Puncture the ear and obtain blood as de- 
scribed in Lesson LV. Hold a cover glass in each hand 




Fig. 45. 
Fig. 45. Showing the way to hold the cover glasses. 

as shown in Fig. 45. With the one held in the left hand 
just touch the center to the bottom of the drop, as in 
Fig. 46, being careful not to touch the ear. Quickly 
place upon it the cover glass held in the right hand as 
in Fig. 47. If the blood is fresh and the glasses clean, 
it will spread rapidly and evenly by capillary attraction. 
The instant it stops spreading seize the upper cover 
glass with the right hand as shown in Fig. 48, and pull 
it quickly apart horizontally. lace the cover glasses, 

276 



PHYSIOLOGICAL HEMATOLOGY. 



277 



smeared side up, to dry. When dry, examine with a 
one-seventh objective. It requires considerable practice 
and skill to make a good spread, although the operation 
seems simple enough. In a good spread, the red cells 




'■/"■ 



Fig. 46. 
Fig. 46. Touching the cover glass to the blood drop. 




Fig. 47. 

Fig. 47. Dropping cover 

glass upon the drop 

of blood. 



Fig. 48. 

Fig. 48. Showing manner of holding the 
cover glass to jerk them apart. 



are evenly distributed, as in Fig. 37. In a poor spread, 
the cells are clustered, and new spreads should be made 
until the desired result is obtained. 



278 



LABORATORY GUIDE IN PHYSIOLOGY. 



4. Precautions.- — Care must be taken to have just the 
proper amount of blood; too little will not spread well 
and too much makes the spread too thick to examine 
well. The blood should not have time to coagulate. The 
cover glass should not touch the ear in obtaining the 
blood. The blood can be made to flow again after it has 
stopped by rubbing the ear briskly with a cloth. 

b. Fixing and staining. 

/. Appliances. — Cover glasses; solution for staining; heater. 

2. Preparation. — Clean cover glasses carefully with soap 
and water, followed by alcohol. Instead of a copper 
plate (Fig. 49) or oven over a Bunsen burner usually 
used in laboratories, a heater as shown in Fig. 50 is rec- 





Fig. .49. 

Fig. 49. Common copper heat- 
ing plate. 



Fig. 50. 
Fig. 50. The water fixing plate. 



ommended. Cover glasses should be dried at boiling 
point, which is constantly maintained in this heater, it 
being filled with water and placed over a burner. There 
is no danger of scorching, as there is on the strip of 
copper over the Bunsen burner. With the pattern and 
dimensions given in Fig. 51, any tinsmith can quickly 
make the heater out of copper. 

(2) Prepare the following solution for staining: 

Ehrlich-Bondi powder (Griibler) 1 gm. 

One-half per cent sol. acid fuchsin 5 c c. 

Aqua dist 25 c.c. 

Let this solution stand one week and filter. 



PH\ T SIOL O GICAL H&MA TO LOG Y. 



279 



J. Operation. 

{a) Obtain and spread blood as described in section a. 

(<5) Place the cover glass, spread side down upon the 
heater and maintain at 100°C. for fifteen minutes. This 
process dries and fixes the preparation. 

(V) Remove the fixed preparation; cover the film with 
staining solution, allowing it to remain from six to ten 
minutes. The time of staining depends upon the 
length of time the film has been heated; a film fixed 
quickly will stain more readily. 




Fig. 51. 
Fig. 51. Plan for constructing the water fixing plate. 

(d) Rinse off the excess of stain in pure water and dry. 
(<?) Mount in balsam. 

Precautions. — Be sure that the water in the heater is 
boiling before placing the films upon it. Do not let 
the water boil too violently or it may boil over and 
spoil the films. The films must be air dried before 
they are placed upon the heater. 



LXII. Differential counting of white cells and of red cells. 

/. Appliances. — Microscope with one-twelfth oil immersion 
lens; mechanical stage (not essential but convenient). 

2. Preparation. — Stain as in Lesson LXI. Write the names 
of varieties of cells, which may become familiar to the 
eye by the study of the colored plate, and as each differ- 
ent cell is discovered, record that fact by a check. 

j. Operation. — Begin at the upper left corner of the speci- 
men and count toward the right the different cells as 
they come into view. When the right border comes 
into view move the specimen so that the adjoining lower 
field is brought into range and count back again. Mark 
the cells found under their proper heads. After the 
observer has become familiar with the different cells he 
can keep in mind the neutrophiles for the entire 
trip across the field, but the others he had best mark as 
soon as found. 

Varieties of leucocytes. (Fig. 52 a.) 
Polymorphonuclear neutrophiles. (Neutrophiles.) 
Myelocytes, 
Small lymphocytes, 
Large lymphocytes, 
Eosinophils, 
Eosinophilic myelocytes. 

Varieties of red cells. (Fig. 52 b.) 
Normoblasts, 
Megaloblasts, 
Microblasts, 
Macrocytes, 
Microcytes, 
Poikilocytes, 
Polychromatiphilic cells. 

280 



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LXIII. Study of bone marrow. 

/. Appliances. — Strong vice; five-eighths inch cover glasses; 
microscope; heater; Ehrlich's triple stain (See Lesson 
LXI) ; section of bone containing red marrow; saw. 

2. Preparation. — Clean cover glasses as usual and have 
water in heater or fixing-plate boiling. 

j. Operation. — Saw a transverse section of bone one inch 
thick. Place it in the vice and turn the handle until the 
bone marrow begins to ooze out on the surface. Just 
touch the surface of this with one of the cover glasses 
and proceed exactly as in exercise LXI a, making as 
good a blood spread as possible. Dry smeared side up. 
Then fix and stain as described in LXI b. Place slide 
under the microscope and make a differential count of 
red and white cells as in LXII. 

4. Precaution. — Have the bone specimen as fresh as possi- 
ble. Saw the piece to be used just before putting it in 
the vice and then take the specimen from the freshest 
side of the bone. 

5. Observations. 

(1) What cells do you find that are not found in normal 
blood ? 

(2) Can you trace these cells to the cells of normal 
blood ? 



261 



PHARMACOLOGY. 



H. AN INTRODUCTION TO PHARHACOLOGY. 
By H. fl. Richter, M. D. 



INTRODUCTORY. 

While the following experiments will more forcibly im- 
press the student's memory with the action of the drugs 
under consideration than any didactic lecture possibly 
could, this must be considered as of secondary importance. 
The real object is to teach pharmacological technique — to 
place the student in a position where he can at any time 
in the future demonstrate experimentally to his own satis- 
faction the activity or inactivity of any drug, and its modus 
operandi. 

With this object in view, experiments have been 
chosen which can readily be performed by the student 
himself. No attempt is made to show the various actions 
of each drug used, but, instead, the most conspicuous and 
easily demonstrated action of each is utilized. Considera- 
ble time is expended on the reflex arc, because the action 
of drugs on its different elements is most readily demon- 
strated. 

Little can be found concerning the doses to be used in 
experiments. In order to save time and trouble, the dose 
to be used in each of the following experiments is given. 

285 



286 LAB OR A TOR Y G U1DE IN PHYSIOL OGY. 

The student is presumed to have a fair working knowl- 
edge of the technique of the physiological laboratory. The 
use of the myograph, kymograph, etc., the setting up of 
electrical apparatus, such as batteries, inductorium, commu- 
tator keys, and the use and effects of same. As to the litera- 
ture on the subject, the following are valuable, and have 
been made free use of: 

Smith's translation of L. Hermann's "Experimental 
Pharmacology " is the only English work devoted to 
technique; Brunton, " Pharmacology, Therapeutics and 
Materia Medica," and "Pharmacology and Therapeutics;" 
White, " Materia Medica and Therapeutics;" Stirling, 
"Practical Physiology;" Landois and Stirling, "Text- 
book of Human Physiology." These comprise most of 
what has been written on the subject in English. 

Each group of students will need the following appar- 
atus and material for the experiments : 
One Daniell cell ; Dog and rabbit holder ; 

Inductorium; Seeker; Pins; 

Myograph; Pin-pointed pipette ; 

Kymograph ; Fine and coarse thread ; 

Contact key ; Normal saline solution ; 

Two frog boards and stands; Gutta-percha tissue; 
Shielded electrodes ; Chloroform ; 

Physiological operating case; Ether (common sulphuric); 
Clippers ; Sulphate of morphin ; 

Hypodermic syringe ; Sulphate of atropin ; 

Commercial curare; Sulphate of strychnin; 

Hydrochlorateof pilocarpin; Ticture of digitalis; 
Sulphate of veratrin ; Sodic carbonate; 

Tincture of aconite ; Sodic sulphate. 



LXIV. Curare. 

i. Material. — One dog; 2 frogs; sodic chloride; curare. 

2. Preparation. 

Prepare following solution of sodic chloride, 0.06 
grms. to 10 c. c. ; curare, 0.1 grm. to 10 c. c. Pith frogs. 
Do not fasten the dog to the board, but simply restrain 
him. Set up inductorium and myograph, the former so 
as to obtain single induction shocks. 

J. Experiments and observations. 

(1) Give a hypodermic injection of 0.02 grm. curare to 
the dog. 

(a) Record the condition of the dog just before, and 
every ten minutes after injections of curare with 
special reference to: 

(I) Muscular activity. 

(II) Respiration — number and depth. 

(III) Circulation — rate and rhythm of heart-beat. 

(IV) Which stops sooner, respiration or circula- 
tion ? 

(£) Formulate the total effect of curare upon the 
animal. 

(2) Ligate the thigh of a frog, except the sciatic nerve, 
near the knee-joint. 

Inject into the dorsal lymph space 0.0012 grms. 

curare. 

(a) What elements enter into the formation of a "re- 
flex arc /" 

(V) What motor phenomena would result from in- 
creased irritability of any part of the reflex arc ? 

{c) What motor phenomena would result from les- 

287 



288 LABOR A TOR Y G UIDE IN PHYSIOLOG Y. 

sened irritability or destruction of any element in 
the reflex arc ? 

(d) What effect has the ligature of the thigh on the 
distribution of the curare ? 

(e) How do the reflex arcs, of which the gastrocnemii 
are the motor ends, differ with regard to the distri- 
bution of the curare ? What part of the reflex arc 
is protected from curare in the ligatured limb ? 

(/) Describe the relative reaction of the gastrocnemii 
to stimuli (chemical, mechanical, electrical) applied 
to various parts of the body and limbs. 

(,£•) Is the sensorium intact? Is it reached by the 
curare ? 

(k) Is the cord intact? Is it reached by curare? 

(3) Expose the sciatic nerves, near the body, in the frog 
used in experiment (2); stimulate them. 

(«) What elements in the reflex arc enter into consid- 
eration in this experiment ? 

(&) Which of these elements are exposed to, which 
protected from the poison ? 

(V) Are both sciatics reached by curare? 

(d) Is there a difference in the reaction of the gas- 
trocnemii to the stimuli applied to the sciatic 
nerves? 

(<?) To what elements of the reflex arc have you lim- 
ited the possible action of the curare? 

(f) Have you proven that curare does not affect the 
nerve trunks? 

(4) Expose gastrocnemii by cutaneous incision. Stim- 
ulate the muscles directly. 

(a) Is there a difference in reaction to stimuli ? 

(£) If a muscle in a poisoned animal reacts to direct 
stimuli, but not to indirect stimuli, though the nerve 
fibers be proven to be intact, on what element in the 
reflex arc must the poison act ? 



PHA RMA COL OGY. 289 

(V) Why would you not use curare as an anaesthetic 
if the poisoned animal does not react to painful 
stimuli ? 

(5) Make two muscle-nerve preparations as described 
on page 56. Dip the nerve of one, and the muscle of 
the other into curare solution. The parts of the 
preparations not immersed should be kept moist with 
normal saline solution. After several minutes mount 
specimens in the myograph. Stimulate the nerves 
and note : 

{a) The relative reaction of gastrocnemii to indirect 
stimulation. 

(<£) Does this bear a resemblance to any previous ex- 
periment ? 

(V) How do results compare with those of previous 
experiment ? 

(6) Stimulate the same muscles directly. 
(#) Relative reaction? 

(<£) Taking this in connection with preceding experi- 
ment, where have you proved that curare acts? 
(V) How do e experiments (5) and (6) compare with 
experiments (3) and (4) ? 
Note: — Failure in experiments (5) and (6) may result 
from insufficient immersion of muscle in curare solution, 
capillary attraction resulting in curare reaching muscle 
supposed to be free from poison, and drying of parts not 
immersed in solution. Of thesethe first is by far the most fre- 
quent cause of failure, the sheath of the muscle rendering 
the absorption of poison a slow process. It may be over- 
come by making a few slight incisions in sheath, or inject- 
ing a drop of the curare solution directly into the muscle. 
Failure of experiment (2), and consequently (3) and 
(4), may result from ligature around thigh being not tight 
enough to prevent diffusion of curare into gastrocnemius. 



LXV. Atropin. 

i. Material. — 2 dogs; atropin sulphate; morphin sulph- 
ate; chloroform (or ether); mask. 
2. Preparation. — Make up following solutions; a strong so- 
lution of atropin 0.4 grm. to 10 c. c.; a weak solution, 
0.02 grams to 10 c. c.; morphin, 0.6 grams to 10 c. c. 
Simply restrain dog " a." Fasten dog "b" to board. 
Give hypodermically, 0.03 grm. morphin to dog "b," 
then anaesthetize him. Set up induction coil so as to 
obtain interrupted current. 
J. Experiments and Observations. 

(1) Drop three drops of the stronger atropin solution 
into one eye of dog " a," allowing them to drop in at 
short intervals, and obstructing tear duct with pressure 
of finger. 

(a) What is the nerve supply of the iris ? 

(b) On what local elements may a drug act to produce 
alteration in size of pupil, and how ? 

(7) Would a drug, acting centrally, though applied 
to one eye, be likely to affect one, or both pupils ? 

(V) Would a drug, acting locally, and applied to one 
eye, be likely to affect one, or both pupils? 

(<?) Would a drug, acting locally on the pupils, but in- 
jected into the circulation, and reaching the pupils 
in this way, be likely to act on one, or both pupils ? 

(/) Are either or both pupils affected by atropin, and 
if so, what effect is produced ? 

(g) Does atropin act locally or centrally to produce 
its effect on the pupil ? 

290 



PHARMA COL OGY. 291 

(k) Can you devise an experiment that would positively 
answer question " g." ? 

(2) Expose the vagus of dog "b" (see pp. 110-111). 
Stimulate it with weak induced current, using shielded 
electrodes. 

(#) What is the function of the cardiac fibers of the 

vagus? 
(<£) How, therefore, would you expect stimulation of 

the vagus to affect rate and rhythm of the heart 

beats ? 
(^r) How would you expect severing of the vagus to 

affect the rate and rhythm of the heart beat ? 
(*/) How do you actually find the rate and rhythm of 

the heart beats affected by stimulation of the vagus? 

(3) Count the pulse, then give 5 mgrm. atropin hypo- 
dermically. 

(a) Count the pulse at short intervals after the injec- 
tion of atropin for at least 30 minutes, or until its 
rate is markedly affected. 

(^) What is the effect of atropin on the rate of the 
pulse ? 

(V) Could atropin produce this effect by acting on the 
vagus center? On the vagus fibers ? On the vagus 
terminations in the heart? On the heart muscle 
direct ? 

(4) After the pulse rate has been markedly affected by 
atropin stimulate vagus as before, using shielded 
electrodes. 

(a) What is the effect on the rate of heart's action? 

(£) Compare this result with that obtained in experi- 
ment (2). 

(<r) Had atropin acted solely by depressing the vagus 
center would we have found a difference in results 



292 LABORATORY GUIDE IN PHYSIOLOGY. 

in stimulating vagus nerve before and after its ex- 
hibition ? 

(d) Had atropin acted on the accelerator apparatus 
would there be a difference in such results ? 

(e) If now, on stimulating the heart muscle directly, 
you obtained a normal physiological effect, to what 
elements have you limited the possible action of 
atropin? 

(/) Basing your opinion on the experiments you have 

performed, to what elements have you limited the 

possible action of atropin? 
(5) Further general observations. 
(#) Take temperature per rectum. 
(£) Note condition of visible mucous membranes, 

with regard to their secretions. 
(7) If dog can be kept until next day, note size of 

pupils. 



LXVI. Pilocarpin. 

/. Material. 

1 rabbit; 1 dog; hydrochlorate of pilocarpin; sulphate of 
morphin; sulphate of atropin; chloroform. 

2. Preparation. 

Make solution of pilocarpin, 50 mgrms. to 10 c.c; atro- 
pin, 0.02 grm. to 10 c.c. ; morphin 0.6 to 10 c.c. 

Do not fasten the rabbit to the holder. Fasten the 
dog to the dog board, after giving preliminary hypoder- 
mic injection of 0.03 grms. morphin. 

J. Experiments and Observations. 

(1) Give, hypodermically, 0.02 grm. pilocarpin to 
the rabbit. 

(a) Record symptoms as they arise, especially as 
regards: 

(I) Secretions; 

(II) Pulse rate; 

(III) Size of pupil; 

(IV) Temperature. 

(£) Formulate the total effect of pilocarpin upon the 
animal. 

(2) After morphinizing the dog, fasten it firmly to the 
dog-board and lightly anaesthetize; expose both vagi. 

Count the pulse. Give a subcutaneous injection of 
0.03 grms. pilocarpin. After salivation has become 
profuse count the pulse again. 

How does pilocarpin affect the pulse rate ? 

(3) Now sever the vagi. 

(a) How does the severing of the vagi affect the nor- 
mal animal? (See page 109.) 
293 



294 LABORATORY GUIDE IN PHYSIOLOGY. 

(o) How does it affect an animal poisoned by pilocar- 
pi? 

(c) Could pilocarpin alter the effect produced by 
severing the vagi if it acted on the proximal side of 
the point at which the vagi were cut? On a point 
beyond that at which they were cut? 

(d) Could the pilocarpin alter the effect normally 
produced by severing the vagi, by acting on the 
cardiac sympathetic? 

(e) Enumerate the possible points at which pilocar- 
pin may act to produce the effects observed. 

(4) Give to the same dog 5 mgrms. atropin, hypoder- 
mically. 

(a) Is the rate of heart-beat altered ? 

(o) Where does atropin act to produce alteration in 

rate of heart- beat (see atropin.) 
(V) Does atropin antagonize the action of pilocarpin 

in this experiment? 
(d) To what elements have you limited the probable 

action of pilocarpin ? 

(5) General observations. 

(#) Compare the action of pilocarpin with that of 
atropin, throughout the range of action observed. 

(o) Is atropin a physiological antagonist to pilo- 
carpin ? 



LXVII. Strychnin. 

i. Material. — One dog; two frogs; sulphate of strychnin. 

2. Preparation. — Make a solution of sulphate of strychnin 
0.01 gm. to 10 c. c; also concentrated solution, 0.2 gm. 
to 10 c. c. Pith frogs. Do not fasten the dog to the 
dog-board. Set up electrical apparatus to obtain tetaniz- 
ing current. 

3. Experiments and Observations. 

(1) Hypodermic injection of 0.01 gm. strychnin to the 
dog. 

(0) Record the condition before, and symptoms as 
they arise after exhibition of the drug, especially 
with reference to : 

(I) Muscular activity. Describe convulsions. 

(II) Respiration. How affected by reflexes. 

(III) Circulation. Rapidity and rhythm of heart. 

(IV) If death occurs, which stops sooner, the 
circulation or respiration ? 

(£) Formulate results. 

(2) Ligate thigh of frog, except sciatic nerve, at junc- 
tion with body. Sever all structures except nerve 
and femur, just below ligature. Separate cut surfaces 
with rubber tissue to prevent diffusion of the drug. 
Turn the frog over and make a median abdominal 
incision. Pressing viscera aside, pick up the sacral 
plexus of nerves going to the uninjured leg. The 
sacral plexus may be readily recognized, lying on each 
side of the median line. Pass a thread loosely around 
the nerves, so as to quickly find them when wanted. 
Inject into dorsal lymph space, 0.0001 gm. strychnin. 

295 



296 LAB OR A TOR V G UIDE IN PHYSIOL OGY. 

(a) What part of the frog is reached by the poison? 
What part protected from it? Illustrate by diagram. 

(£) Were strychnin a convulsant through its action 
on the sensorium, would the legs be equally con- 
vulsed ? If it acted on the spinal cord ? If it acted on 
the motor nerves? If it acted on the muscles directly? 

(V) Are both legs convulsed ? 

(d) To what parts in the reflex arc have you limited 
the action of the strychnin ? 

(3) Using as a guide the thread formerly passed around 
it, pick up sacral plexus and sever it high up. 

(#) Does the strychnin reach the motor nerve and 
muscles of uninjured leg ? 

(£) If strychnin were a convulsant through its action 
on either the motor nerves or the muscles, or both, 
would the uninjured leg still participate in the con- 
vulsions ? 

(c) Demonstrate that muscles, sciatic nerve and sacral 
plexus below the point at which it was severed, are 
still intact, by stimulating distal portion of latter. 

(d) To what elements of the reflex arc have you lim- 
ited the possible action of strychnin ? 

(4) Expose the heart of a frog and ligate the aortae at 
the base. Operation as follows : 

Freely expose sternum by -f- shaped incision and laying back of 
flaps. Remove lower half of sternum with scissors, taking care not to 
injure vessel in abdominal wall which comes just to tip of sternum. 
Freely incise exposed pericardium, bringing heart into view. Grasp 
apex of heart with forceps, taking care not to use force enough to cut 
through ventricular wall, and draw heart down and forward. This gives 
ready access to bulbus arteriosus and aortse. With an aneurism needle 
pass fine thread around latter, taking care not to injure auricles, and 
ligate. 

With scalpel cut through occipito-atlantoid membrane, from side to 
side, and bend head forward. Remove posterior wall of upper end of 



P HARM A CO LOG Y. 297 

spinal canal by inserting smaller blade of strong scissors into spinal canal 
and cutting, taking care not to injure cord. Allow a drop of the concen- 
trated solution of strychnin to fall directly upon cord; or with fine 
hypodermic needle inserted 1.5 cm. into the arachnoid space inject two 
drops of the solution. 

(a) What effect has ligation of the aortae on the cir- 
culation ? 

(<£) Would stoppage of the circulation prevent the 
drug from reaching the peripheral terminations or 
trunks of the sensory nerves? Motor nerves? Muscles? 

(V) Where then, must strychnin act to produce the 
observed symptoms ? 

(//) Would cessation of the circulation delay the ac- 
tion of strychnin on the cord by slowing the rate of 
its absorption by the latter ? 

(5) After observing results in experiment (4), destroy 
first the upper then the lower portion of the cord, by 
passing a wire down the spinal canal. 

{a) How does destruction of the upper part of the 
cord affect the convulsions ? 

(<£) What is the result of the destruction of the en- 
tire cord ? 

(<r) Do the results agree with those of previous ex- 
periments ? 

Note : — Destruction of the upper part of the cord 
during the preparation of the animal may take 
place; if so, the upper limbs will not take part in 
the convulsions. 

(6) Further observations and comparisons. 

(a) Compare the general effects of strychnin and 
curare in the dog. 

(<£) Compare results obtained in experiments consist- 
ing of ligating the thigh of a frog except the sciatic 
nerve, and injecting, in the one case strychnin, in 
the other curare. 



LXVIII. Veratrin. 

/. Material. — Sulphate of veratrin; 1 dog; 3 frogs. 

2. Preparation. 

Prepare a solution of veratrin, 50mgrms, to 10 c.c. Pith 
frogs. Restrain dog, but do not fasten to board. Set 
up myograph and induction coil, the latter arranged 
for single induction shocks. 

j. Experiments and Observations. 

(1) Give a subcutaneous injection of 15 mgrm. veratrin 
to the dog. 

{a) Describe symptoms as they arise. 
(<£) Summarize. 

(2) Place thread around the sacral plexus of the pithed 
frog so as to easily find it, as described under 
strychnin. Inject 0.003 gms. veratrin into dorsal lymph 
space. 

(a) Describe symptoms referable to rexflexes. 

(£) Note particularly the difference between a forcible 
contraction and a prolonged contraction. 

(3) Sever the sacral plexus around which the thread 
has been passed. 

{a) How do the contractions of the legs in response 
to direct stimuli compare? 

(b) Has severing the sacral plexus altered the dura- 
tion of the contraction of the muscles supplied? 

(V) If veratrin still produces its typical effects, to 

what elements in the reflex arc have you limited its 

action ? 
(d) Compare the effect of severing the sacral plexus 

in a frog poisoned with veratrin with that in a frog 

poisoned with strychnin. 

298 



PHARMA COL OGY. 299 

(4) Ligate the thigh of a pithed frog at the junction 
with the body, not including in the ligature the sciatic 
nerve. Sever all tissues just below the ligature ex- 
cept the nerve and the femur. Carefully separate 
the cut surfaces with rubber tissue so as to prevent 
diffusion of the drug. Inject 0.003 gm. veratrin into 
the dorsal lymph space. 

(#) By means of a diagram show the distribution of 
the poison. 

(£) Compare the contractions of the legs, noting par- 
ticularly the difference in the duration rather than 
the difference in the force of the contraction. 

(V) If the protected limb reacts normally to stimuli, 
to what elements in the reflex arc have you limited 
the possible action of veratrin? 

(d) Compare results with similar experiment with 
strychnin. 

(5) From the frog used in experiment (4) make two 
gastrocnemii preparations. Fasten in myograph by 
means of femurs, and stimulate them directly, making 
tracings of contractions. 

(a) Compare tracings. 

(fr) To what elements have we limited the action of 

veratrin ? 
(V) Suggest an experiment which would limit the 

action to one element. 

(6) Very cautiously sniff veratrin. Describe the sensa- 
sation. 

(V) General observations and comparisons. 

(a) Review your notes on the action of curare, strych- 
nin and veratrin upon the reflex arc. 

(b~) How would you prove that a drug paralyzed by 
its action on the spinal cord? 

(V) How would you prove that a drug destroyed reflex 
activity by its action on some part of the sensorium? 



LXIX. Digitalis. 

Material. — Tr. digitalis ; sulphate of morphin ; sodic 
chloride; chloroform; two dogs; one frog; sodic sul- 
phate {j4 sat. sol.). 

Preparation. — Make solution of morphin, 0.6 gm. to 
10 c. c. Sodic chloride, 0.06 gm. to 10 c. c. Pith 
frog. Morphinize dogs, using 0.03 gm. and chloroform 
them previous to operation. Set up induction coil so as 
to obtain tetanizing current, having contact key in 
primary circuit. Prepare kymograph for tracing. 
Experiments and Observations. 

(1) Fasten a dog firmly to the dog board and lightly an- 
aesthetize. Expose the vagus. Count the pulse. Using 
shielded electrodes and separating secondary from 
primary coil, find a current just weak enough not to 
affect heart when applied to vagus. Now inject 0.0 
c. c. tr. digitalis subcutaneously. After waiting at 
least 20 minutes, in the meantime using no anaesthetic 
except a repetition of the morphin if necessary, and 
keeping the wound closed after moistening with saline 
solution, stimulate the vagus with same current that 
before the exhibition of digitalis was unable to affect 
the heart. 
{a) What is the function of the cardiac fibers of the 

vagus? 
{If) What result is produced by the stimulation of 

these fibers in the normal animal? 
{c) Does digitalis increase or decrease the excitably 

of the vagus? 
{d) With the stimulus applied to the vagus fibers and 
300 



PHA RMA CO LOG Y. 301 

the cardiac fibers carrying impulses centrifugally, 
could this altered excitability be due to central 
action of the digitalis? 

(2) After morphinizing dog, fasten firmly to dog board 
and lightly anaesthetize; expose femoral artery. 

Having placed mercury in the manometer, and 
filled the cannula, connecting tube and short arm of the 
manometer with y 2 saturated sodic sulphate solu- 
tion, to prevent clotting, insert the cannula into the 
femoral artery, in a direction toward the heart. There 
must be no air bubbles in the apparatus at any point. 
Let the float, carrying the tracing point, rest on the 
mercury in the long arm of the manometer and record 
on the revolving drum. 

The anaesthetic should be discontinued as soon as 
the cannula is inserted into the femoral artery. Take 
normal tracing. Now give the dog0.6 c. c. tr. digitalis 
hypodermically. 

(a) Watch effect on elevation of float, making trac- 
ings at short intervals. 
(£) What elements enter into arterial tension ? 
(V) How does a " high tension " tracing differ from 

a "low tenison " tracing? 
(d) How do changes in tension affect the elevation 

of the tracing above the abscissa ? 
(<?) What effect has digitalis on arterial tension ? 

(3) Having firmly fastened a pithed frog to frog board 
with web stretched over a cover glass fastened into a 
hole in the board by means of sealing wax, focus the 
microscope upon a certain arteriole in the field, and 
measure its diameter with an eyepiece micrometer. 
Now inject into dorsal lymph spaces 0.3 c. c. tr. digi- 
talis and measure same arteriole at intervals of 10 



302 LABOR A TOR Y G UIDE IN PHYSIO LOG Y. 

minutes. Keep the web moist with normal saline 
solution. 

(a) What change occurs in the diameter of the arteriole? 
{b') What effect would you expect this to have on ar- 
terial pressure ? 

(V) Would its action on the arterioles help to account 
for its effect on arterial pressure? 
(4) Comparisons. — Compare digitalis and atropin with 
regard to (a) their effect on the rate of the heartbeat. 

(b) Their effect on the irritability of the vagus. 



LXX. Aconite. 

i. Material. — Tr. aconite; sulphate of atropin; 1 dog; 1 

frog; sphygmograph. 
2. Preparation. 

Make solution of atropin, 0.02 grms. to 10 c.c. Pith 
frog. Do not fasten the dog to the dog board. 
5>. Experiments and Observations. 

(1) Give 1 c.c. tr. aconite hypodermically to the dog. 
Record symptoms as they arise. 

(2) Fasten the pithed frog on its back to the board. 
Count the heart beats, exposing heart, if necessary. 
Now give 0.2 c.c. tr. aconite subcutaneously. What 
effect has aconite on the pulse rate ? (To obtain satis- 
factory results observations must be made at short 
intervals, for from 30 to 60 minutes.) 

(3) After the pulse has been markedly affected, inject 
into the dorsal lymph spaces 0.0002 grm. atropin. 
Does atropin affect the pulse rate after administration 
of aconite? 

(4) Take a sphygmographic tracing, of the radial 
pulse of a student. Note the pulse rate. Administer, 
by mouth, 0.2 c.c. tr. aconite and 0.06 c.c. every 10 
minutes until action on pulse is noticeable. Repeat 
tracing and counting of pulse at short intervals. 

(a) How does aconite affect blood pressure ? 

(£) How is the rate of the heart's action affected? 

(7) What subjective sensations are produced ? 

(5) Comparisons. — Compare aconite and pilocarpin with 
regard to their action on the gastro-intestinal system. 



APPENDIX. A. 



APPENDIX A. 



i. Normal saline solution. 

This solution, or as it is also called normal salt solu- 
tion or physiological salt solution, is so much used in the 
physiological laboratory that it should be made in consid- 
erable quantity and always easily accessible. 
Formula: 

Common salt (C. P.) 30 gms. 

Distilled water 5 L. 

It is convenient to keep the solution in a siphon bottle. 
It is thus protected from dust and evaporation, and is al- 
ways easily accessible. See Fig. 53. 




Fig. 53. 
Fig. 53. Siphon-bottle for normal saline solution. 

2. Frog boards. 

There is probably no more satisfactory or economical 
frog board than a piece of dressed soft pine 15 cm. by 30 

307 



808 LAB OR A TOR V G U1DE IN PH YSIOLOG Y. 

cm., and one or two centimeters in thickness. Some prefer 
to use cork boards which come in pieces 10 cm. by 25 
cm. and % cm. in thickness. 

3. The physiological operating case. 

A convenient case, and one which will be sufficient 
in the simple experiments presented in this book, contains 
the following instruments : 

1 medium scalpel, 

1 small scalpel with narrow blade, 

1 medium scissors, 

1 microscopic scissors, 

1 medium dissecting forceps, 

1 microscopic forceps, with curved, serrated jaws, 

2 serre fine forceps, with stiff spring and serrated jaws, 
1 groove director and aneurism needle, 

1 silver probe, 

1 blunt needle, for pithing frogs, 

2 dissecting needles. 

The case may be of leather or leatherette. Such a 
case may be used nearly as much in the histological as in 
the physiological laboratory. 

4. Galvanic ceils. 

For general use in the physiological laboratory there 
is probably no galvanic element superior to the Daniell 
cell (named after Prof. J. F. Daniell, of King's College, 
London). Much the most convenient and economical 
size is the quart or liter cell whose porous cup measures 
5-6 cm. in diameter and 10 to 12 cm. in height. If more 
current is needed than is furnished by one of these cells it 
is very easy to join two or more of them into a battery. 

In large laboratories it will be found expedient to de- 
vote an old table to the galvanic cells. This table should 



APPENDIX A. 309 

be provided with a supply of copper sulphate and of 10% 
sulphuric acid in large siphon bottles similar to the one 
suggested for normal salt solution (Fig. 53), except that 
instead of the short tube for equalizing pressure one may 
insert a filter through which at the end of the laboratory 
period the student may return the liquids. 

The accumulation of zinc sulphate in the acid makes 
the renewal of the acid necessary from time to time. The 
deposit of metallic copper upon the copper plate reduces 
the copper sulphate solution in strength. It may be kept 
replenished by an excess of crystals of that salt in the large 
supply jar. A very practical method of amalgamating the 
zinc plates is to have a jar containing 10% sulphuric acid 
with mercury in the bottom; as the plate is immersed the 
acid attacks it and cleans it so that the mercury readily 
clings to it and may be rubbed over the surface with a 
cloth. Another method, which is preferred by some, is as 
follows: Dissolve 7 5 gms. of mercury in a mixture of 150 
c. c. strong nitric acid and 300 c.c. strong hydrochloric 
acid. Add to the solution 450 c.c. of strong hydrochloric 
acid. Keep this amalgamating solution in a ground glass 
stoppered jar. To amalgamate a zinc plate one need only 
dip it for a few moments into the solution, remove it, rinse 
under the spigot and rub with a cloth. 

At the end of each laboratory period the cells should 
be emptied, the zinc plates rinsed and drained, and the 
porous cups left in a tray of running water, or at least in 
a considerable excess of water. 

5. To curarize a frog. 

In experiments on the irritability of muscle tissue it is 
necessary to, in some way, suspend the activity of the 
irritable nerve fibers which are supplied to every muscle. 
In certain other experiments it may be advisable to thus 



310 



LABORATORY GUIDE IN PHYSIOLOGY. 



remove the influence of the nervous system. Curara — 
also spelled curare, curari, urari, and woorara, woorari, 
wourali, etc., — an arrow poison used by the South Amer- 
ican aborigines, is the means usually employed to accom- 
plish the end desired. The way in which curare exerts its 
influence, is made the subject of study in another place. 
Make a 1% solution by pulverizing 1 gramme of commer- 
cial curare, and dissolve it in 100 c. c. of distilled water. 
It need not be filtered unless intended for use with a 
hypodermic syringe. If kept in a ground glass stoppered 
bottle, in a cool place, it will retain its efficiency for 
months. 

The most convenient method of curarizing a frog is to 
inject with a narrow pointed pipette, 1-3 drops of the 
solution, through a minute ventral cutaneous incision. 

The drug will begin to take effect in a few minutes. 
The maximum effect may be delayed some time. 



6. To prepare the kymograph for work. 

Remove the cylinder, stretch a sheet of the prepared 
glazed paper tightly upon the surface, place it upon such 
a stand as the one shown in Fig. 54; set the drum to 




Fig. 54. 



Fig. 54. 
Drum support for use in smoking the kymograph drums. 



rotating and bring the triple gas flame under the drum. In 
a few moments it will be evenly covered with a film of 



APPENDIX A. 311 

carbon which is as sensitive to touch as a photographer's 
plate is to light. 

7. A fixing fluid for carbon tracings. 

Gum damar 160 gms. 

Benzole q. s. ad 2000 c.c. 

If this solution be kept in a large museum jar in the 
laboratory, the removed sheet bearing the tracings may be 
dipped in toto or it may be subdivided and dipped in sec- 
tions. Let the tracing be lowered quickly into the solu 
tion and after a few seconds taken out and drained. If it 
be now laid upon a sheet of filter paper — or a newspaper — 
it will be dry in a few minutes. 

8. The cardiograph. 

Any laboratory will have different forms of cardio- 
graphs for demonstration purposes, but not every labora- 
tory is able to afford numerous duplicates. 
An expert tinsmith will make the tam- 
bour pans at very moderate cost, and the 
student can do all the rest. Pans may 
be made of two sizes No. 1, diameter 
FlG 55> 5 cm., depth 4 mm., outside diameter of 

tube 3 to 4 mm., length of tube 3 to 4 cm. No. 2, dia- 
meter 4 cm., depth 3 mm., tube as in No. 1, see Fig. 55, 
To make the cardiograph : — Take a tambour pan No. 1, 
stretch thin sheet rubber — the dentists' "rubber dam," and 
sold as such by dealers — across the pan and tie in place 
with thread, A few drops of sealing wax will keep the 
thread in place after it is tied. Mount the tambour as 
follows : From any well seasoned, close-grained hard- 
wood in boards, about 1 cm. thick, cut small triangular 
pieces about 10 cm. on a side. In the center of each tri- 
angle bore a hole to receive a medium sized cork (about 





312 LABORATORY GUIDE IN PHYSIOLOGY. 

1.5 cm. in diameter) the upper edges of the triangle 
may be beveled and each corner may be furnished with a 
leg by screwing into each corner from the lower surface, 
a round headed screw, leaving about 1 cm. of the screw 
out to serve as the leg. If the class is large, the demon- 
strators should prepare these tambour boards in advance. 
The tambour is mounted by fitting a cork to the hole 
in the tambour board, boring the cork and pressing the 
tambour tube through the 
hole from below upward. Fix 
a button of cork to the mem 
brane with sealing wax. The 

completed cardiograph will 

, . Fig. 56. 

present in section the rela- 
tions shown in Fig. 56. As will be seen from the cut, 
the position of the button may be varied by varying its 
shape or by changing the adjustment of the tambour tube 
in the cork. The cardiograph tambour is the receiving 
tambour. 

g. Tambours. 

It is probable that no part of the laboratory equipment 
is more in use than the various forms and adjustments of 
the tambour. The possibilities of this device were first 
brought out and developed by Marey, Director of the 
Physiological Institute of the Ecole des Hautes Etudes 
en Sorboune, Paris. 

If the laboratory cannot afford to furnish at least one 
pair of the Marey tambours to each table, recourse may 
be had to such a device as that just described above under 
the cardiograph. Such simple tambours when carefully 
constructed prove most satisfactory. 

To construct a recording tambour : Use a No. 2 tambour 
pan, stretch the rubber less tightly than for the receiving 



APPENDIX A. 313 

tambour and mount similarly in a triangular tambour 
board, omitting the screw legs. Make a recording needle 
like the frog's heart lever, except that the foot, which rests 
upon the middle of the tambour membrane, should pre- 
sent a larger surface. The cork which forms the fulcrum 
of the lever should be fixed to the tambour board in such 
a position that the long arm of the lever is vertically above 
a diameter of the tambour. Any change of pressure upon 
the air in the tambour will cause the membrane to rise or 
fall, thus producing in the tracing point of the lever a cor- 
responding rise or fall, differing from that of the membrane 
only in its greater extent. It is evident that if the tube of 
the receiving tambour be joined to the tube of the record- 
ing tambour through a thick rubber tube any movements 
which affect the button of the first will be manifested by a 
rise or fall of the lever which rests upon the second. 

10. The stethograph. 

In order to record graphically the movements of the 
chest one may use various mechanical devices. The most 
simple device, and a most effective apparatus, when only 
the time relations and the character of the movements are 
matters of concern, is the instrument which involves the use 
of two tambours, a receiving and a recording tambour. 
The latter is the one describedab ove, (9.) 

A receiving tambour may be constructed especially for 
this purpose as follows : Let a tinsmith construct, from 
small brass wire, (}4 — % mm. in diameter), spiral springs 
which shall present the outline of truncated cones (See 
Fig. 57 a), and fit inside the larger tambour pans. 

If the student be supplied with tambour pans, spring, 
"rubber dam," thread, sealing wax and cork, he may con- 
struct his receiving tambour by placing the spring in the 



314 



LABORATORY GUIDE IN PHYSIOLOGY. 



tambour pan, stretching the sheet rubber 
over the spring, tying and sealing. The 
now conical diaphragm of the receiving 
tambour should be provided with a cork 
button, and adjusted by passing its tube 
through a horizontal hole near the end of 
one of the wooden rods (see Fig. 18). 
Connect the tambours by means of a small rubber tube. 

ii. The thoracometer. 

If one wishes to measure the extent of the movements 
of the thoracic walls the stethograph, for mechanical 




Fig 57. 




Fig. 58. 

Fig. 58. Receiving button for Thoracometer — an instrument for use in 

quantitative determination of variations in thoracic diameters. 

reasons too apparent to need enumeration here, affords, in 
the height of the recorded waves, unreliable data. To 
make a quantitative determination of the variation of any 
diameter of the thorax requires the application of a differ- 
ent principle. The following method has been success 
fully used: Construct the apparatus shown in the accom- 
panying cut, using for the spiral spring brass wire 1.5 to 2 
mm. in diameter. The cone defined by the spring should 
be 6 or *7 cm. across the base and should have an altitude 
from the base to the contact surface of the hard rubber 



APPENDIX A. 



315 



button of about 4 or 5 cm. It may be fixed to the hard 
wood or fiber base with three staples and the base in turn 
fixed, as indicated in the figure, to an iron rod about 1 cm. 
thick by 30 cm. long. A hole is bored through the base in 
the middle of the cone. A pulley whose plan and elevation 
are given in Fig. 58 b and c, fastened to the under surface 
of the base serves to change the direction of a cord which 
is tied to a ring in the hard rubber button. 

12. The be!t=spirograph. 

The apparatus here described was contrived to over- 
come as far as possible the objections which may be raised 




Fig. 59. 
Fig. 59. The Belt-spirograph for quantitative determination of varia- 
tions in chest girth. 

to the previously used instruments for this purpose. Note 
in the first place that the wide elastic belt will follow faith- 
fully eyery movement of the chest wall, not sinking into 
the soft tissues during inspirations; second, the almost in- 
elastic fish cord will transmit the movement of the thorax 
much more accurately than elastic air inclosed within 
elastic conductors. 

The 59 a, b and c figures show the construction of 
the belt spirograph: (a) The 2-3 cm. wide, elastic belt 



316 



LABORATORY GUIDE IN PHYSIOLOGY. 



showing location of pulleys, (b) A section of thorax 
showing belt in position. The cord is tied to an eye in 
pulley No. 1, passes around the circuit of pulleys to No. 1 
again, thence over two or three pulleys which serve to 
change the direction, bringing the cord finally to a record- 
ing lever adjusted as described for the thoracometer. 
(c) Showing an enlarged view of a pulley. The brass 
base of each pulley is fixed to a piece of sole leather 4 or 5 
cm. long by 3 or 4 cm. wide. Copper wire, riveted at the 
points r and r', clasps the elastic belt and holds the pulley 
in position. 

13. The stethogoniometer. 

Various methods have been employed for determining 
the curvature of the chest wall. Even so simple a method 




Fig. 60. 

Fig. GO. The Stethogoniometer used in graphically recording any 
perimeter of the thorax. 

as the taking of several diameters will reveal approx- 
imately the general conformation of the chest wall. A 
graphic method has this to recommend it : that a glance at 
an outline of any circumference of the thorax reveals more 
than any amount of time expended in the study of numer- 
ical data. Of all the graphic methods used by the writer 
the one here described seems most simple and practical. 
The accompanying figure (Fig. 60) shows the instrument, 
which will be recognized as similar to a draftsman's pan- 



APPENDIX A. 



317 



tograph. As used by the draftsman such an apparatus 
enlarges figures by any multiple from 1 to 5 in linear di- 
mensions, for that purpose the tracing stilus is placed at 
a and the recording pen or pencil at b, while the point c is 
fixed to the table. As used to trace the curvature of any 
line in the body, the recording pencil is fixed at a, while 
the point b is made to follow the curved surfaces under 
observation. In this way records of one-fifth the linear 
dimensions of the curve traced may be recorded. Such rec- 
ords are compact and readily filed for subsequent reference. 



14. The pneo=manometer. 

This instrument may be easily con- 
structed in the laboratory. Take a piece 
of heavy glass tubing of 7 to 9 mm. lumen 
and at least 160 centimeters in length. 
Bend it as shown in Fig. 61. A covered 
filter may be attached as shown in the 
figure if there is any tendency for the 
mercury to be thrown out. 

15. The chronograph. 

For many experiments, especially upon 
the circulation or respiration, it is neces- 
sary to trace upon the rotating drum, along 
with the record of the circulatory or respi- 
ratory movement, a record of time in 
seconds or known fractions thereof. In- 
struments for this purpose are to be had 
from the instrument houses. 

If the student or demonstrator is in- 
clined to construct his own chronograph 

the accompanying figure and description 
The Pneo-mano- , , . & & , . r - \_. 

meter. For test- may be of assistance to him. (bee .big. 
ing pressure in Q2.~) 
forced respiration. 



Fig. 



318 



LABORATORY GUIDE IN PHYSIOLOGY. 



Materials and Construct ion. — (1) A soft iron electro- 
magnet (m) with soft iron armature (a), as shown in 
A. A machinist or electrician can construct these from 
strictly pure, soft Swedish iron. 

(2) No. 24 double silk covered copper wire, to be wound 
as indicated in A (x to y). The wire should be wound 
in three layers and when the winding is complete it 
should present the appearance shown in Fig. 62 B, m\ 

(3) From fiber board or from wood one may construct 
such a lever and magnet support, as shown in Fig. 60 
B. The lever (1) is pivoted at f; the block a' bears 
the armature; the counterpoise (w) may be adjusted 




Fig. 62. 
Fig. 62. The Chronograph. 

so as to make the part of the lever at the right of f 
slightly heavier than that at the left, so that when no 
current is flowing through the electro-magnet the 
armature is lifted from the magnet. 

(4) A check (c) rests upon an adjustable screw (s) and 
limits the excursion of the lever. 

(5) A straw may be fixed with wax to the end of the 
lever and a tracing point (p) of parchment paper 
slipped into the straw. 

(6) The wires from the clock or the chronograph sys- 
tem are connected at x' and y'. 



APPENDIX A. 3 if) 

(7) The base may be clamped to a support and the 
tracing point adjusted to any height or direction. 
This simple chronograph may be made sufficiently deli- 
cate to record ^-seconds accurately, though seconds or 
half seconds will usually answer the purposes of the gen- 
eral experiment. For very small divisions of a second the 
tuning fork should be used. 

To set up a simple chronograph. — Join the chronograph 
and the contact clock or a metronome in continuous circuit 
with a common Daniell cell. The clock makes contact 
every second or fraction, the armature is drawn down by 
the electro-magnet and thus records the time upon the 
drum of a kymograph. 

16. The chronographic system. 

If many students are working at the same time and at 
the same experiment in a laboratory, it is unnecessarily 
costly in both money and space for each student or group 
of students to be supplied with separate chronographic 
clocks and batteries. One clock and a battery of several 
cells can be employed to run ten or twelve chronographs. 
Such a chronographic system is too simple to require ex- 
tended description. 

(1) Bowditche's interruption clock or Petzold's simple 
contact clock may be hung in any convenient place in 
the laboratory and brought into circuit with 

(2) A battery, in series, whose strength must depend 
upon the amount of external resistance to be overcome, 
i. e., the number of chronographs in the system. 

(3) The chronographs must be all in one general circuit 
rather than upon branches from a primary circuit. 

(4) A loop of the general circuit may pass to each 
table and the chronograph inserted in the loop. It is 
hardly necessary to remind the demonstrator that if, 



320 LABOR A TOR Y G UIDE IN PHYSIOL OGY. 

for any purpose, a chronograph be removed from a 
table when the system is in operation, the general 
circuit must be instantly completed by use of a con- 
nector. 

17. To prepare 10% hydrochloric acid, the acidum hydro= 
chloricum dilutum of the U. S. P. 

The concentrated, c.p., hydrochloric acid of a sp. gr. 
of 1.16 contains 31.9 per cent by weight of HC1 gas. To 
prepare 10% HC1, take 31.4 c.c. of the concentrated acid 
and dilute with distilled water to 100 c.c. From this di- 
lute HC1. 0.2% HClor0.1% HC1 or any other desired 
strength below 10% may be readily obtained. 



APPENDIX B. 



APPENDIX B. 



On the general plan of a course in physiology and the 
equipment of a laboratory. 

The following pages are reprinted from a report of the 
committee on syllabus, representing the Association of Ameri- 
can Medical Colleges. The committee ivas in session Feb. 
15-18, 1896, Chicago. 

The course in physiology. 

The course in physiology should be continued through 
two years and should be, in a general way, coordinated 
with the course in comparative anatomy and general 
biology and histology. By coordination in this connection 
is meant the arrangement of the courses in such a way 
that the student shall learn first the more fundamental and 
general and then the more special. To teach the student 
the physiology of the liver one year and the gross and 
minute anatomy of that organ the next year must be recog- 
nized by all as an inversion of the logical order. To 
teach the anatomy of an organ one year and its physiology 
the next year puts the teachers of both these branches 
at considerable disadvantage, and the chances are great 
that the student will have a less clear comprehension of 
the subject presented in this way than he would if the 
interval elapsing between the study of the more general 
branch and the more special branch be a short one. 

Every course in physiology should be accompanied 
by laboratory exercises in which the student may fami- 

323 



334 LABORATORY GUIDE IN PHYSIOLOGY. 

liarize himself with the technique of the subject and may 
demonstrate for himself the more fundamental facts of this 
science. The laboratory exercises should be coordinated 
with the recitations and demonstrations as far as it is pos- 
sible to do so. 

The first half of the first semester (eight weeks") should 
be spent in a study of the physiology of the cell as il- 
lustrated in unicellular plants and animals. While the 
student is studying the morphology of the protococcus, 
the yeast cell, the amoeba and the paramoecium in the 
biological course he may profitably study the physiology of 
these organisms from such a text as, " The Cell" (Hert- 
wig), and should repeat in the laboratory the experiments 
mentioned in Hertwig's book. " Allgemeine Physi- 
ologie " (Max Verworn, Jena, 1895) is a valuable help to 
the instructor who is conducting such a course. 

The second half of the first semester may be spent on 
muscle-nerve physiology. Having already studied the 
reaction of amoeba and paramoecium to electricity, and hav- 
ing studied, in general histology, the structure of muscle 
fibers and cells, and nerve fibers and cells; further having 
made careful dissections of frogs and other vertebrate ani- 
mals the student is in a position to comprehend and appre- 
ciate the reaction of muscle tissue in response to various 
direct stimuli and to indirect stimuli applied to the nerve. 
The frog-heart and the "muscle-nerve preparation" are 
most used for such experiments. 

Beginning with the second semester or second half of 
the first year the general subject of nutrition should be be- 
gun. Whether one introduces this field of physiology 
with the study of the circulatory system or of the digestive 
system is a matter of little consequence. The problems 
of the circulation being, for the most part, physical prob- 
lems, would seem to justify the consideration of that sub- 



APPENDIX B. 325 

ject first, followed by the respiratory system, which pre- 
sents simple problems in mechanics, physics and chem- 
istry. The student, having in the meantime made some 
progress in physiological chemistry, is able to comprehend 
the general features of the chemical problems involved in 
digestion, and should now enter upon a systematic consid- 
eration of nutrition : 1, food and foodstuffs; 2, prepara- 
tion of foods; 3, mastication; 4, deglutition; 5, salivary di- 
gestion; 6, gastric digestion; 7, intestinal digestion; 8, ab- 
sorption; 9, distribution; 10, assimilation or anabolism; 11, 
katabolism and animal heat, and 12, excretion. This course 
will probably consume the second semester of the first year 
and a part or all of the first semester of the second near. 
The remaining time allotted to physiology should be de- 
voted to the physiology of the nervous system, the phys- 
iology of the special senses, and the physiology of repro- 
duction. All of these courses should be accompanied by 
laboratory work. 

After the student has completed the above required 
courses he should be given an opportunity to elect special 
courses in physiology during the second semester of the 
second year and during the third year. Profitable elective 
courses would be, for example: 1. Physiology of intra- 
uterine life, following Preyer's " Physiologie des Embryos;" 
2. Special problems in the physiology of digestion, follow- 
ing Brunton in "Handbook for the Physiological Labora- 
tory; " 3. Physical examinations of the blood, using hema- 
tokrit, hemometer, corpuscle counter, micrometer and 
staining methods; 4. Experimental physiology of the cen- 
tral nervous system, following Cyon; 5. Physiological 
psycholog} 7 , following Wundt or Ladd. The instructor 
may get much help from such works as Cyon's "Methodik 
der Physiol. Experimente; " Gscheidlen's " Physiologische 
Methodik;" Foster and Langley's ''Practical Physiol- 



326 LABORATORY GUIDE IN PHYSIOLOGY. 

ogy; " Schenck's " Physiologisches Practicum; " Brunton 
and Burdon-Sanderson's u Handbook of the Physiolog- 
ical Laboratory;" McGregor-Robertson's "Physiological 
Physics;" Langendorf's " Physiologische Graphik," and 
Stirling's "Practical Physiology." 

The organization and equipment of the department of 
physiology. 

Inasmuch as many of the colleges of the Association 
have not yet established physiological laboratories, it is 
thought well to give a few general hints on the subject. 
The imposing equipments which one sees in the physiolog- 
ical institutes of Europe, equipments which, in the 
aggregate, have cost many thousands of dollars, over- 
awe one and make one hesitate to advise the undertaking 
of so great a task, so we are letting the years slip by with- 
out establishing physiological laboratories. We must not 
forget that the equipment of European laboratories is a 
growth which has covered many, decades; and further, 
that it is really advisable to allow a department to grow, 
collecting, in the course of a few years, an equipment 
which is perfectly adapted to the wants of the institution 
and to the special methods of the head of the department. 
The committee strongly advises the early establishment 
of physiological laboratories, even if an institution cannot 
appropriate for the purpose more than $1,000 to start 
with. If an institution can devote to this department a 
well-lighted general laboratory room 36 ft. to 40 ft. square, 
with two or three small rooms for instrument room, work- 
shop and library, and can appropriate $1,000 to $1,500 for 
the first equipment, then a laboratory fee of $5 annually 
from each student who works in the department will, in 
the course of a, decade, produce a sufficiently full equip- 
ment for all practical purposes. 



APPENDIX B. 327 

At this point it may be well to give a hint as to the 
organization of the department, as this determines largely 
the character of the equipment and the number of dupli- 
cations of each instrument. 

The amount of personal supervision required by the 
student in practical physiology is so great that it is in- 
expedient to attempt to conduct large classes. A demon- 
strator and one assistant demonstrator cannot properly 
supervise the work of more than thirty students at one 
time, even though each student be provided with a labora- 
tory manual. In the organization and equipment here 
planned let it be understood that the laboratory class work 
in sections of thirty students each, and that each section be 
subdivibed into ten divisions of three students each. Now, 
experience in many laboratories has shown that a student 
will accomplish practically as much in one laboratory 
period of three hours as in two laboratory periods of two 
hours each. The three-hour laboratory period promotes 
economy both for the student and for the department. 
Following this arrangement, two instructors would be able 
to supervise the work of 180 students, meeting one sec- 
tion of thirty students each day. With this allotment of 
time each student would have three hours of laboratory 
work each week during the year, which would enable him 
to demonstrate for himself all of the fundamental princi- 
ples of physiology. In the question of the choice between 
(1) the condensation of 180 hours of laboratory work in 
physiology into a period of sixty days with three hours per 
day, and (2) the distribution of the same number of hours 
over sixty weeks (two years'") with three hours per week, 
and its coordination with theoretical work in physiology 
and with the courses in gross anatomy and histology, we 
would, without a moment's hesitation, decide in favor of 
the latter plan. 



328 LA BORA TOR Y G UTDE IN PHYSIO LOG Y. 

If this general plan of organization be adopted, and if 
the department wishes to provide for sections of thirty 
students, working in ten divisions of three students each, 
then the apparatus should be duplicated in tens. The fol- 
lowing list of apparatus is suggested as a practical one 
with which to make a beginning : * 

EQUIPMENT FOR GENERAL LABORATORY WORK. 

10 strong tables, 6 feet by 3 feet, $5 00 $ 50.00 

10 kymographs, $33 350.00 

20 Daniell's cells, quart size, $1.75 37.50 

4 pounds of copper wire, No. 18 double cotton cover, 50c. . . . 2.00 

y 2 pound copper wire, No. 24 double silk cover, $2 00 1.00 

10 simple compasses (for detectors), 30c 3.00 

10 contact keys, $1.25 12.50 

10 Du Bois keys, $3.25 32.50 

10 simple rheocords, $2.50 25.00 

10 Du Bois Reymond induction machine?, $17.50 175.00 

10 Pohl's commutators, with crossbars, $4.50 45.00 

10 pairs of tambour pans, $2.00 20 00 

20 heavy-base stands, $1.00 20.00 

Fixtures for same — 

2 right angle clamp-holders, extra heavy $0.50 

1 universal clamp-holder 0.75 

1 extension ring (1 inches) 0.25 

1 Muscle forceps, cork insulation 1.00 

1 simple myograph 2.50 

10 of each $5.00 50.00 

10 Bunsen burners, 35c 3.50 

10 bell jars, 80c 8.00 

10 double-valve rubber bulbs, largesize, 50c 5.00 

5 haemometers (Fleischl's), $12.50 62.50 

5 sphygmographs. $20.00 100.00 

5 blood corpuscle counters (Zeiss), $17.50 87.50 

*In reprinting the following list the author has taken the liberty to 
revise his earlier list as published in the report of the committee. As 
revised it provides for a higher class of apparatus at a proportionately 
higher price, but brings the aggregate down to the former estimate by 
reducing the number of incidentals, 



APPENDIX B. 329 



General surgical appliances, forceps, shears, etc 

10 pounds assorted sizes of glass tubing, 35c 

Assorted sizes of soft rubber tubing 

Rubber stoppers, assorted sizes, perforated 

Corks and sheet cork 

Cork borers, Files, for cutting glass tubing 

2 gas generators, Kipp's, $3.50 

Graduated cylinders, pipettes, flasks, bottles, beakers, etc. 



25.00 


3.50 


3.00 


2.00 


2.00 


2.50 


7.00 


25.00 



$1,160 00 

INSTRUMENTS FOR SPECIAL USE AND FOR DEMONSTRATIONS. 

Detector $ 2.50 

Galvanometer 50.00 

Rheostat or plug resistance box of 12 coils 10.00 

Metronome, mounted to make and break circuit 12.00 

Contact clock 25.00 

Tuning fork, electrically maintained, mounted for tracing 25.00 

Chronograph 10.00 

Haematokrit 25. 00 

Plethysmograph 6.50 

Quantitative balances 30 00 

1 pair dog scales 15.00 

Laboratory balances 10.00 

Mercurial manometer for blood pressure. 10.00 

Ludwig rheometers 15.00 

Moist chamber 20.00 

Muscle forceps 3. 50 

Capillary electromometer (Kiihne's) 5.00 

Du Bois-Reymond rheocord 25.00 

Hot air motor 40.00 

Still for making distilled water 15.00 

Drying oven, 10x12, double wall 13.00 

Apparatus for determining focal distances 2.50 

Steel-calipers 5 00 

Spirometer 10.00 

Stethogoniometer, belt spirograph and pneomanometer 15.00 



$400 00 
This list might easily be extended to amount to several 
thousand dollars, but it is intended here to include only 
those instruments which seem necessary to start with. 



380 LA BORA TOR Y G UIDE IN PHYSIO LO G Y. 

THE WORK SHOP. 

Demonstrators and students can easily construct in a 
shop, many pieces of simple apparatus, which if pur- 
chased of some instrument house, would amount to many 
times the cost of the material and would deprive students 
of some very valuable experience. Frog, rat, rabbit and 
dog holders may be made, the tambour frames may be 
furnished with membranes and mounted as receiving or 
recording tambours, cardiographs, or stethographs. All 
writing levers, electrodes, etc., should be made by the 
students. A room with bench and vice and $25 for car- 
penter's and machinsts' tools would be an ample start. 

A FEW NECESSARY CHEMICALS. 

20 pounds CuS0 4 $ 1 40 

10 pounds H 2 S0 4 75 

5 pounds mercury 3.30 

2 pounds kaolin (for electrodes, etc.) 10 

1 dram of curare 1. 25 

5 pounds gum da mar 1.25 

20 pounds benzol 4.00 

10 pounds chloroform (imported duty free) 5 00 

10 pounds sulphuric ether (imported duty free) 3 00 

5 pounds unmedicated surgical cotton at 25 cts 1.25 

2 pounds sealing wax in sticks 1 .00 

5 pounds plaster of Paris 50 

5 gallons alcohol (96$) 

1 gallon abs. alcohol 

2 pounds sodium hydrate 

2 pounds magnesium sulphate 

2 pounds sodium chlorid (pure) 

2 pounds glycerin 

1 pound hydrochloric acid , 

1 pound nitric acid 

1 pound ammonium hydrate 

Drugs as listed under Pharmacology 



About $35.00 



APPENDIX B. 331 

A WORKING LIBRARY OF PHYSIOLOGY. 

Beside the laboratory manuals enumerated' under the 
" Course in Physiology," we mention a few journals and 
general works that should be in every laboratory of physi- 
ology : Hermann's " Handbuch der Physiologie"; Journal 
of Physiology, ed., Michael Foster, Cambridge, England; 
Pfluger's, Archive f. d. gesammte Physiologie, Bonn, Ger- 
many; Archil t fur Anatomie and Physiologie, [physiol. part] 
ed., Du Bois-Reymond, Berlin, pub.,. Veit & Co., Leipsig; 
Centralblatt fur Physiologie, pub., France Dauticke, Leipsic; 
Journal of Experimental Medicine [physiological part edited 
by Bowditch, Chittenden and Howell], D. Appleton & 
Co.; " Animal Physiology," Mills, D. Appleton & Co., 
1889; "Text-book of Physiology," Michael Foster, Mac- 
millan, 1888 93;" '-Human Physiology," Landois and 
Stirling, Blackiston, Philadelphia, last edition; " Refrac- 
tion and Accommodation of the Eye," Landolt, Lippin- 
cott, Philadelphia, 1886; "The Frog," Marshal], London, 
1894; "Anatomy of the Frog," Ecker, Oxford, 1889 ; 
" The Cat," Mivart, Scribner, 1881; "Dissection of the 
Dog," Howell, Holt &Co., 1888; "Anatomie des Hundes," 
Ellenberger & Baum, Berlin, 1891 ; "Dictionary of Medi- 
cine," (4to), Gould, Blackiston, Philadelphia, 1895. 

Beside these there should be recent representative 
manuals of histology, general biology, embryology, chem- 
istry and physics. 

PHYSIOLOGICAL CHEMISTRY. 

It has been taken for granted that the chemical prob- 
lems of physiology will be assigned to the department of 
chemistry. The equipment of that department makes such 
a division of the subject highly advantageous. For years 
urine analysis has been taught, usually in the second year 
of the course in the department of chemistry. Many of 



332 LAB OKA TOR Y G UlDE IN PH YSIOL OGY. 

the stronger institutions have long since expanded the sec- 
ond year course in chemistry into a very creditable course 
of physiological chemistry, beginning with an investiga- 
tion of foodstuffs, following this with qualitative and 
quantitative work on the chemistry of digestion, and de- 
voting the last semester of the second year to the analysis 
of urine. The best laboratory manuals on the subject are : 
Long's " Laboratory Manual of Chemical Physiology," 
Colegrove & Co., Chicago, 1895; Stirling's "Practical Phys- 
iology" (first part); Halliburton's "Essentials of Chemical 
Physiology'" Longmanns, Green & Co., 1893. The phy- 
siological library should contain also : " Text-book of 
Chemical Physiology and Pathology," Halliburton, Long- 
manns, Green & Co., 1891 ; "Physiologische Chemie," 
Bunge, Vogel, Leipzig, 1894 ; " Lehrbuch d, physiologisch, 
Chemie," Neumeister, Gustav Fischer, Jena, 1893; "Phy- 
siological Chemistry," Hammarsten, Wiley & Sons, New 
York, 1893; "Physiological Chemistry of the Animal 
Body, "Gamger, Macmillan, 1893; " Chemical Physiology 
and Pathology," Hoppe-Seyler. 



APPENDIX C. 



APPENDIX C. 



It is proposed at this point to devote a few pages to the 
illustration and brief description of the more important 
instruments and glassware which go to make up a prac- 
tical equipment for a physiological laboratory. 

i. Physical Apparatus.* 

1. The Kymograph. — The basis of the instrumentarium of the 
physiological laboratory is the kymograph. It is in almost con- 




Fig. 1. Kymograph. 



*For the plates in this section I am indebted to the Chicago Lab- 
oratory Supply and Scale Co., 29 West Randolph St., Chicago. 

335 



336 



LAB OR A TORY G UIDE IN PH YSIOL OGY. 



stant use in muscle-nerve physiology, in circulation, in respiration, 
and in pharmacology. It must be portable, durable, accurate, read- 
ily adjustable as to speed and height of drum. All of these quali- 
ties, together with reasonable cheapness, are possessed by the kym- 
ograph illustrated in the accompanying figure. This instrument 
was designed by Mr. C. H. Stoelting, of Chicago, for use in the 
physiological laboratory of the University of Chicago. It is now 
used in the University of Michigan, Northwestern University, Mas- 
sachusetts Institute of Technology and the State Universities of 
Illinois, Texas and Colorado, in Rush Medical College, and the 
Detroit Medical College. 

The height of the instrument is 55 cm.; weight 15 ko. The 
drum is propelled by a clockwork, which is under perfect control 
of the operator. 




Fig. la. 
Fig. a. Drum supporter with drum and burners. 



2. The Myograph, a. The spring myograph, modified from Du 
Bois Reymond's. b. Simple myograph as used in the physiological 
laboratory of the Northwestern University, and shown in Fig. 2. 
c The crank myograph. 



APPENDIX C. 



387 




Fig. 2. 

3. The Chronograph time-marker. Figure 4 shows Dr. Lingle's 
modification of Pfief s single chronograph. 




Fig. 3. 



338 LAB OR A TOR Y G UIDE IN PHYSIOL OGY. 



4. The Marey Tambour. See Fig. 4. 




Fig. 4. 
5. The Pohl Commutator. See Fig. 5. 




Fig. 5. 

6. The Introduction Coil or Inductorium. Figure 6 shows 
DuBois-Reymond's instrumen). Ludwig's instrument consisted in 
changing the axia of the coils to the vertical position and counterpoising 
the secondary coil. The DuB-R. instrument, or some modification of it, 
is in more general use, and is satisfactory. 



APPENDIX C. 



339 




Fig. 6. 




Fig. 7. 




Fig. 8. 



7. The Muscle Forcips. a. Figure 8 snows a fine brass instru- 
ment with insulated jaws and a binding post, b. A simpler and cheaper 
form, with cork insulation, and without the binding post, answers all 
ordinary purposes. 

8. The Detector, or low resistance galvanometer, is shown in 
Figure 8. 

8a. The Galvanometer, a, Eblemann's universal; b. Rosenthal's 
physiological. 



340 



LAB OR A TOR Y G VIDE IN PHYSIOLOG Y. 
A p , j 5"ocm 




Fig. 10. 
10. The Compensator. Ludwig's instrument is shown in figure 10. 





Fig. 11. Fig. 11a. 

11. Batteries, a. The Daniell cell, or element, is shown in fig- 
re 11. b. The Bichromate cell — see figure 11a. 



APPENDIX C. 



341 




Fig. 12. 

12. The Rheocord. h. Dubois-Raymond's Rheocord. b. The 
simple rheocord as shown in figure 12. c. The Oxford rhecord. 




t o. 



Fig. 18. 

13. Electrodes. Figure 13 shows: a. Hand-electrodes of insu- 
lated copper or platium wires for use with induced currents, b. Non- 
polarizable electrodes, variously constructed. For description see text. 



342 



LABORATORY GUIDE IN PHYSIOLOGY. 






Fig. 14. Fig. 14a. Fig. 14b. Fig. 14c. 

14. Binding Posts. Various forms are shown above. 

15. Binding Connectors. Constructed of brass, and in varying 
forms. 





Fig. 16. 



Fig. 16a. 



16. Keys. a. DuBois-Reymonds key with knife-edge contact. 
b. The mercury key, as shown in figure lGa. c. The spring contact key 
(Fig. 12K). d. The Morse key. 



APPENDIX C. 



343 






Fig. 17. 




Fig. 17a. 



Fig. 17b. 



17. Anthropometric Instruments. These are various and consist 
of scales, meter tape, calipers, dynamometers, spirometer, etc., etc. 
Fig. 17 shows the belt-spirograph used to make a quantitative deter- 
mination of variations of chest girth. Fig. 17a shows the pneo-manom- 
eter for testing forced respiratory pressure. Fig. 17b shows the 
stethogoniometer, for making a graphic record of the chest perimeter. 



344 



LABORATORY GUIDE IN PHYSIOLOGY 





Fig. 18. 



Fig. 19. 



18. Still. For making distilled water. 

19. Support. Special pattern for physiology, with extra heavy 
base length 50-75 cm., weight %]i Ko.-4>£ Ko. 




Fig. 20. 



20. Drying Oven, with double wall 10 in. by 12 in. May be used 
for incubator in experiments in digestion. 



APPENDIX C. 

II. Chemical Apparatus. 



345 




Fig. 27. 



©QQ@ #©©(§(§) f|) H)| 




Fig. 28. 

27. Analytical Balance, Becker's short beam, for a charge up to 
100 g. in each pan. Sensitive to ^ mg. with rider apparatus. 

28. Analytical weight, Becker's, 100 g. down. 

*For the plates in this section I am indebted to Richard & Co., 108 Lake St., 



346 



LABORATORY GUIDE IN PHYSIOLOGY. 




Fig 29a. 




^^^ggBasaiHiHi^i^ ^^ 



Fig. 29b. 



29a. Balance for laboratory work. Capacity, 2 pounds. Sensitive 
to 1-20 grain. 

29b. Weights 500 g. down, in polished block. 



APPENDIX C. 



347 




Fig. 30. Fig. 31. Fig. 32. 



Fig. 33. 



Fig. 34. 



Fig. 35. 



30. Gay Lussac's burette, on wooden base, 25 c. c. in 1-10. 
31a. Mohr's burette, w. pinchcock, 50 c. c. in 1-5. 
31b. Mohr's burette, w. pinchcock, 100 c. c. in 1-5. 

32. Graduated cylinders with lip, double graduation, 10 c. c, 50 
c. c, 100 c. c, 250 c. c , 500 c. c, 1,000 c. c. and 2,000 c. c. 

33. Graduated cylinders, stoppered, 100 c. c, 500 c. c. and 1,000 
c. c. 

34. Volumetric flask, 1,000 c. c. 

35. Bottle for mixing, glass stoppered, 250 c. c, 500 c. c, 1,000c. c. 



348 



LABORATORY GUIDE IN PHYSIOLOGY. 






Fig. 36. 



Fig. 37. 



Fig. 38. 



36. Evaporating dishes in nests of 9, from 2 oz, to 20 oz. 

37. Evaporating dishes, best German porcelain, heavy rim, nests 
of five, from J4 to 1 gal. 

38. Flasks, vial mouth. 





Fig. 39. 

39. Beakers, plain' 3 oz. -50 oz. 

40. Beakers. Griffin, lipped, 5 oz.-64 oz. 



Fig. 40. 



APPENDIX C. 



349 






Fig. 41. 



Fig. 42. 



Fig. 43. 



41. Glass funnels, best German, 2 in. to 8 in. 

42. Glass funnels, ribbed, 3j^ in. to 8 in. 

43. Liter Erlenmeyer flasks, Jena glass. 






Fig. 44. 



Fig. 45. 



Fig. 46. 



44. Calcium chloride tubes, Schwarz,4-4. 

45. Potash bulbs, Geissler's, with drying tube. 

46. Woulf-bottles, 1 pint size and 1 qt. size. 



350 LAB OR A TOR V G UIDE IN PHYSIOL OGY. 





Fig. 47. Fig. 48. Fig. 49. 

47. Bell glasses, low form, with knob, 6 in. diam. 

48. Bell glasses, tall form, with knob, 1% in. diam. 

49. Bell glasses, open top, 6 in. diam. 





Fig. 50. Fig. 51. Fig. 52. 

50. Bell glass, open top, with tubulure at side, l / 2 gal. 

51. Bottles, extra wide mouih, 4 oz. to 16 oz. 

52a. Bottles, mushroom, glass stopper, narrow mouth, 4 oz. to 
16 oz. 

52b. Bottles, mushroom, giass stopper, narrow mouth, 16 oz. 



APPEFDIX C 



351 



53. T-tubes. 

54. Y-tubes. 

55. Kipp's gas generator, 1 qt. 

56. Thermometers, 150 degrees C. 



fi 




Fig 53. 





Fig 54. 



Fig. 55. 



Fig. 56. 



INDEX 



PAGE 

Abreast, arrangement of cells. . 35 

Absorption 189 

Accommodation 3 . 216 

range of 238 

Acetic acid in gastric digestion. 173 

Aconite 303 

Acuteness of vision 232 

Adaptation of eye for direction . 219 

for distance 216 

Adipose tissue, action of gastric 

juice on 172 

Age, effect on range of accom- 
modation 211 

Albumin, preparation of acid 

albumin 162 

preparation of egg alb 161 

Alcohol, effect on ciliary motion 22 

Amalgamation of zinc 27 

Amperes, unit of current 31 

Amplitude of convergence 241 

Amylolytic ferment 187 

Anaesthesia. Ill 

Anelectrotonus 76 

Anode 28 

Anode Pole, influence of 51 

Anthropometric data 127 

Appendix A 307 

Apex beat. 91 

Apparatus for determining focal 

distances 202 

Arterial pressure 1 04 

Astigmatism 237 



PAGE 

Atropin 290 

Average vs. median value 128 

Batteries 308 

grouping 34 

Belt spirograph 315 

spirograph 118-121 

Bile pigments, Gmelins test for. 186 
Bile, preliminary experiments 

on 185 

Biuret test 164 

Binocular fixation 220, 242 

Blind spot 223 

calculate size of 223 

map out 223 

Blood pressure, influenced by 

digitalis 301 

laws of 102 

Blood, examination of fresh... 259 

Blood corpuscle counter 261 

Bone marrow, study of 281 

Break induction shock 71 

Bread, action of saliva upon. . . 158 

Brush electrodes 52 

Calipers 124 

Capacity of Lungs 124 

Carbon-dioxide gas, effect on 

ciliary motion 21 

determination of 1^0 

Carbohydrates 153-156 

Cardiogram 92 

Cardio-pneumatogram 139 

Cardiograph 91 

353 



351 



INDEX. 



PAGE 

Cardiograph 311 

Cardinal points of simple di- 
optric system 207 

Cells, galvanic 308 

Cell, work done by. 29 

Chemical stimulation 60 

Chloroform, effect on ciliary 

motion . . . 21 

Chronograph 317 

system 319 

Ciliary motion 16 

Circulation, capillary 85 

Circulatory system, artificial. . . 102 

Circuit, short and long 40 

primary and secondary. .. . 70 
Citric acid in gastric digestion. . 173 

Conjugate focal distances 203 

Color sense 238 

perimeter . . 230 

Commutator, Pohl's (Fig. 5). . . 28 
Compensator, Ludwig (Fig. 8) . 46 
Constant current, stimulation 

with 68 

Convergence 210, 221 

amplitude of 241 

to measure 241 

negative 245 

Counting white corpuscles 265 

red corpuscles 262 

red and white corpuscles. . 268 

Curare , 287 

Curarize a frog 309 

Current, polarizing 76 

how measured 31 

change of course 29 

change of direction 28 

Curvature, radius of 201 

Daniell cell 27 

Data, anthropometric 127 

evaluation of 127 



PAGE 

Data, grouping of 127 

preservation of 125 

Descending current 68 

Detector (Fig. 6) 35 

Dextrin, properties of 154 - 1 55 

Diameters of chest 124 

Diaphragm, action of 132 

tactile observation of 133 

Diffusibility of fat-derivatives. . 184 

of proteids 166 

Digestion and absorption, intro- 
duction 150 

salivary 157 

gastric 171 

Digitalis 300 

influence on blood prts. .. . 301 

Dilute hydrochloric acid 320 

Dioptric system (Fig 29, A)... 207 

Direct vs. indirect stimulation. . 26 
Discharge of liquids through 

tubes 95 

relation of to resistance. . . 95 

Dissection of eye 192 

Distance, pupillary 244 

Dyne 24 

Elastic tubes, flow of water in. 98 

Elasticity of rabbit's lung 138 

Electrical units 31 

Electricity as a stimulus 65 

Electrodes (Fig. 9) 52 

Electrolysis, a measure of E. 

M. F 30 

Electromotive force, how meas- 
ured 31 

Electrodes, positive and nega- 
tive 28 

Electrotonus 75 

laws of 79 

Emmetropia 237 

Emulsion 183 



INDEX. 



355 



PAGE 

Ecdosmotic equivalent . . 191 

Endosmotic pressure 190 

Energy, electrical , 30 

Erg 24 

Ergs of muscle work 74 

Ether, effect on ciliary motion. 22 

Evaluation of data 127 

Eye, adaptation of for distance. 216 
adaptation of for direction . 219 
application of laws of re- 
fraction to 210 

dissection of 192 

the reduced 211-212 

to locate cardinal points in. 212 

skiascopic 247 

Extra polar region 16 

Extract of pancreatic ferments. 185 

Far point 218 

Falling bodies, law of 94 

Fats, emulsification of 183 

Fats, saponification of 182 

Fat-splitting ferment 187 

Fehling's solution 153 

Ferment 18G 

amylolytic 187 

fat-splitting 187 

milk-curdling 187 

proteolytic 187 

Fixation binocular 220-242 

monocular 219 

Fixing fluid for tracings 311 

Fixing the spread, hematology. 278 

Flow of liquids through tubes. 93, 98 

Focal distances, conjugate. .... 203 

apparatus for determining. 201 

Focal distance of lenses 201 

Form sense, to test 234 

Fovea centralis, shadows of... 225 

Frog-boards 307 



PAGE 

Frog's heart-beat, graphic rec- 
ord of 89 

Frog's heart, the action of 87-89 

Frog's thigh, anatomy of 57 

Galvanic cells 308 

Galvanismus 75 

Gastric digestion, influence of 

NaCl on 177 

influence of mechanical di- 
vision on 178 

influence of temperature en 179 

steps of ISO 

active factors of 172 

acid factor of . . . 173 

Gastric juice, preparation of.. 171 

Standard. . , 175 

Gastrocnemius preparation. ... 57 

Girth of chest 124 

Glass, to measure index of re- 
fraction 200 

Gmelin's test for bile pigments. 186 

Hand electrodes 52 

Hematology, microscopic tech- 
nique 276 

Haematocrit ) 271 

Hematology 257 

Haemogloblin, estimation of . . . 273 

Haemometer, Fltischl's 273 

Heart-sourj.ds 91 

Height 125 

Holder, for rabbit (Fig. 19) 110 

Hydrochloric acid in gastric di- 
gestion 173-174 

influence of on putrefaction 177 
Hydrochloric acid dil., to pre- 
pare 320 

Hydrogen, respiration in 145 

Hyperopia 237 

Illuminating gas, respiration in, 148 



356 



INDEX. 



PAGE 

Images, Purkinje-Sansom's. . . . 223 

Impulse wave 99 

Inelastic tubes, flow of water in, 98 
Index of refraction of water. . . 199 

of glass 200 

instrument for determ.... 199 

Induction shock, make 70 

break 70 

Intermittent pressure, influence 

of 98 

Intestinal digestion 185 

Intra-abdominal pressure 114 

Intra-polar region i6 

Intra-thoracic pressure 114 

to measure. 116 

Kaolin forelectrodes 51 

Katelectrotonus 76 

Kathode 28 

Kathode pole, influence of. ... 51 

Key, Du Bois-Reymond (Fig. 4) 29 

simple contact, (Fig.-7-K ). 43 

the mercury, (Fig. 3. ) 29 

Kymograph 62 

to smoke Drum 310 

Lactic acid in gastric digestion. 173 

Lactose, properties of 155, 156 

Law of contraction, Pfliiger's. . 80 

of electrotonus. 79 

of falling bodies '. . . 94 

of kathodic and anodic in- 
fluence 55 

of Torricelli 94 

Lenses, focal distance of 201 

Leucocytes, varieties of 280 

Lever, for transmitting dia- 
phragm movements 133 

Lenses, numeration of 232 

Light, perimeter 229 

Light, sense 237 



PAGE 

Liquids, flow of through tubes 

93-98 

Lung capacity 124 

Macula lutea 225 

Maltose, properties of 155,-156 

Make induction shock 70 

Manometer, mercurial 103 

Marriotte's experiment 223 

Maxwell's experiment 225 

Mechanical stimulation 59 

Median value 128-129 

Mercurial manometer 103 

Meter-angle of convergence. . . 244 
Millon's reagent, preparation of 162 
Milk, chemistry of 167-170 

gastric digestion of 180 

Milk-curdling ferment 187 

Monocular fixation 219 

Movements, respiratory ....... 113 

Multiple-arc, arrangement of 

cells 35 

Muscle-nerve preparation 56 

Muscle-telegraph, Du Bois-Rey- 
mond. 48 

Myograph, double (Fig. 10) 53 

simple (Fig. 13) 59 

Myopia 236 

range of accommodation in 239 

Myosin, preparation of 161 

Narcotics, influence on ciliary 

motion 16 

Near point 218 

Needle, saddler's for hasmatol- 

ogy 259 

Nitric acid test 163 

Nitrogen, generation of .... 147-148 

respiration of 147 

Nonpolarizable electrodes 52 

Normal saline solution 307 



INDEX. 



357 



PAGE 

Numeration of Lenses 232 

Ohms, unit of resistance 31 

Olein 183 

Operating case 308 

Ophthalmoscope 247 

Ophthalmoscopy 247 

Optics, physiological 198 

Osmosis 189-191 

Palmitin 183 

Pancreatic ferments, glycerin 

extract of 185 

Pancreatic juice, action of 186 

artificial 185 

Pepsin, glycerine extract of. . . . 171 

possible dilution of K5 

Peptone, to separate from other 

proteids 165 

diffusibility of 167 

Perimeter, instrument 226 

circles 228 

chart 230 

Perimetry 226 

Pfliiger's law of contraction. ... 70 

Pharmacology 285 

Phosphoric acid in gastric di- 
gestion 173 

Photometer 237 

Phrenic nerve, dissection of.... 134 

Phrenogram 132-134 

Phenograph 132 

Physiological operating case. . . 308 

Piezometer 96 

Pilocarpin 293 

Pith, to pith a frog 16 

Plane, inclined, for computing 

ciliary work 24 

Plates, positive and negative. . . 28 
Plasma and corpuscles, relative 

volume 270 

Pneomanometer 125 



PAGE 

Pneomanometer 317 

Pneumantogram 136 

Pohl's commutator 28 

Polarizing current 76 

Poles, positive and negative-. . . 28 

Preparation, gastrocnemius. ... 56 

sartorius 61 

Pressure, arterial 104 

endosmotic 1 90 

formulae 104-105 

intermittent 98 

intra-abdominal 1 14-116 

intra-pulmonary 137 

laws of blood pressure 102 

of liquid in tubes 96 

respiratory - 137 

venous 104 

Proteids, diffusibility of 166 

coagulation of 162 

properties of 161 

tests for 163-164 

Proteoses, diffusibility of 167 

Proteolytic, ferment . .... 167 

Pulmonary vagus 137 

Pulse 106 

impulse wave 99 

Punctum proximum 218 

remotum 218 

Pupillary distance 244 

Purkinje-Sansom's images 223 

Rabbit board (Fig. 19). 110 

Rabbit's lungs, elasticity of . . . . 138 

Radial artery, location of 106 

Radius of curvature 201 

Range of accommodation 238 

Reaction changes in fatigued 

muscles 74 

Red blood corpuscles, varieties 

of 280 

Red corpuscles, counting 262 



358 



INDEX. 



Red and white cells, differential 

counting of 280 

Reduced eye 211 212 

Reducing sugars, tests for 155 

Rennin 181 

Reservoir 93 

Resistance, central and distal. . 97 

how measured 31 

Resistance, relations of to dis- 
charge 95 

Respiration 11-3 

in closed space H4 

in C0 2 gas 145 

N-gas 148 

H-gas 148 

under abnormal conditions 141 

in abnormal media 147 

Respiratory movements 113 

in man 118 

pressure 133 

quotient 143 

Rheocord, DuBois-Reymond's. 40 

simple (Fig. .7) 43 

Rheonom, Fleischl's 48 

Rheostat 40 

Saccharose, properties of. . 155-156 

Saline solution (0.6#) 307 

Salivary digestion 157-161 

Saponification 182 

Sartorius preparation 61 

Scheiner's experiment 222 

Series, arrangement of cells in. 35 
Siphon bottle for solutons 

(Fig. 53) 307 

apparatus for forcing gas. . 20 

Skiascopic eye 247 

Skiascopy 252 

Sodic chloride (0.6$) 307 

Snellen's test type 233 

Sphygmograms 106 



PAGE 

Sphygmographs. 106 

Spirometer 124 

Spreading blood, haematoh gy. . 278 

Staining blood 278 

Standard gastric juice 175 

Starch, digestion of 158 

properties of 153 

Stearin 183 

Stethograph 118 1 19. 313 

Stethogoniometer 118, 123, 316 

Stethoscope 91 

Stimulants, influence of on cil- 
iary motion 16 

Stimulation, chemical 60 

direct 26 

indirect 26 

of vagus 112 

mechanical 59 

thermal 60 

variations of .62 63 

Strychnin ■ 295 

Syntonin, preparation of 161 

Tandem, arrangement of cells. 36 

Tambours, receiving 312 

recording 312 

Tape, meter 124 

Test types, Snellen's 233 

Thermal stimulation 60 

Thoracometer 118, 120, 314 

Thorax, contour of 123 

Toisson's solution 268 

Torricelli, law of 94 

Tracings, fixing fluid for 311 

Tromer's test 157 

Tubes elastic, flow of liquids 

through 97 

flow of liquid through 93 

inelastic, flow of water in. . 98 

Units electrical 31 

Vagus nerve, action of 109 



INDEX. 



359 



PAGE 

Vagus nerve, pulmonary 137 

stimulation of 112 

Value, median 128-129 

Velocity of flow of liquids 74 

Venous pressure 104 

Veratrin 298 

Vision 192 

acuteness of 232 

Visual angle 233 

Volts, unit of electro-motive force 31 



PAGE 

Water element 65 

to measure index of refrac- 
tion of water 199 

Wave, pulse or impulse 99 

Weight 125 

White corpuscles, counting. . 265 

Work done by cilia 24 

done by a muscle 73 

Xanthroproteic test 164 

Yellow spot : 225 







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UBRA RY OF CONGRESS 




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